diff --git a/changelog.d/4298.bugfix b/changelog.d/4298.bugfix
new file mode 100644
index 0000000000..4da2ff899b
--- /dev/null
+++ b/changelog.d/4298.bugfix
@@ -0,0 +1 @@
+Fixing missing F-Droid notifications when in background due to background syncs not triggering
\ No newline at end of file
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/Session.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/Session.kt
index d4bfd4ee8c..dfe43aed6f 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/Session.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/Session.kt
@@ -120,9 +120,11 @@ interface Session :
     fun requireBackgroundSync()
 
     /**
-     * Launches infinite periodic background syncs
-     * This does not work in doze mode :/
-     * If battery optimization is on it can work in app standby but that's all :/
+     * Launches infinite self rescheduling background syncs via the WorkManager
+     *
+     * While dozing, syncs will only occur during maintenance windows
+     * For reliability it's recommended to also start a long running foreground service
+     * along with disabling battery optimizations
      */
     fun startAutomaticBackgroundSync(timeOutInSeconds: Long, repeatDelayInSeconds: Long)
 
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncService.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncService.kt
index 9480cc73f1..c17b31b910 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncService.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncService.kt
@@ -105,9 +105,8 @@ abstract class SyncService : Service() {
                 }
             }
         }
-
-        // It's ok to be not sticky because we will explicitly start it again on the next alarm?
-        return START_NOT_STICKY
+        // Attempt to continue scheduling syncs after killed service is restarted
+        return START_REDELIVER_INTENT
     }
 
     override fun onDestroy() {
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncWorker.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncWorker.kt
index b81804feb5..41bb1a44a6 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncWorker.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/job/SyncWorker.kt
@@ -121,9 +121,9 @@ internal class SyncWorker(context: Context,
                     .setBackoffCriteria(BackoffPolicy.LINEAR, WorkManagerProvider.BACKOFF_DELAY_MILLIS, TimeUnit.MILLISECONDS)
                     .setInitialDelay(delayInSeconds, TimeUnit.SECONDS)
                     .build()
-
+            // Avoid risking multiple chains of syncs by replacing the existing chain
             workManagerProvider.workManager
-                    .enqueueUniqueWork(BG_SYNC_WORK_NAME, ExistingWorkPolicy.APPEND_OR_REPLACE, workRequest)
+                    .enqueueUniqueWork(BG_SYNC_WORK_NAME, ExistingWorkPolicy.REPLACE, workRequest)
         }
 
         fun stopAnyBackgroundSync(workManagerProvider: WorkManagerProvider) {
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/BackgroundDetectionObserver.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/BackgroundDetectionObserver.kt
index 7cc00d023f..a12587ac56 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/BackgroundDetectionObserver.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/util/BackgroundDetectionObserver.kt
@@ -29,7 +29,7 @@ import javax.inject.Inject
 @MatrixScope
 internal class BackgroundDetectionObserver @Inject constructor() : LifecycleObserver {
 
-    var isInBackground: Boolean = false
+    var isInBackground: Boolean = true
         private set
 
     private
diff --git a/vector/src/fdroid/AndroidManifest.xml b/vector/src/fdroid/AndroidManifest.xml
index 3a7c107138..022b08f16d 100644
--- a/vector/src/fdroid/AndroidManifest.xml
+++ b/vector/src/fdroid/AndroidManifest.xml
@@ -1,9 +1,11 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     package="im.vector.app">
 
     <uses-permission android:name="android.permission.WAKE_LOCK" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <!--
     Required for long polling account synchronisation in background.
     If not present ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS intent action won't work
@@ -24,6 +26,11 @@
             android:enabled="true"
             android:exported="false" />
 
+        <service
+            android:name=".fdroid.service.GuardService"
+            android:exported="false"
+            tools:ignore="Instantiatable" />
+
     </application>
 
 </manifest>
\ No newline at end of file
diff --git a/vector/src/fdroid/java/im/vector/app/di/FlavorModule.kt b/vector/src/fdroid/java/im/vector/app/di/FlavorModule.kt
new file mode 100644
index 0000000000..39b5c4a976
--- /dev/null
+++ b/vector/src/fdroid/java/im/vector/app/di/FlavorModule.kt
@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2021 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.app.di
+
+import android.content.Context
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import im.vector.app.core.services.GuardServiceStarter
+import im.vector.app.fdroid.service.FDroidGuardServiceStarter
+import im.vector.app.features.settings.VectorPreferences
+
+@Module
+@InstallIn(SingletonComponent::class)
+abstract class FlavorModule {
+
+    companion object {
+
+        @Provides
+        @JvmStatic
+        fun provideGuardServiceStarter(preferences: VectorPreferences, appContext: Context): GuardServiceStarter {
+            return FDroidGuardServiceStarter(preferences, appContext)
+        }
+    }
+}
diff --git a/vector/src/fdroid/java/im/vector/app/fdroid/BackgroundSyncStarter.kt b/vector/src/fdroid/java/im/vector/app/fdroid/BackgroundSyncStarter.kt
index 7221e2b065..0fe89e7fe5 100644
--- a/vector/src/fdroid/java/im/vector/app/fdroid/BackgroundSyncStarter.kt
+++ b/vector/src/fdroid/java/im/vector/app/fdroid/BackgroundSyncStarter.kt
@@ -27,9 +27,8 @@ object BackgroundSyncStarter {
     fun start(context: Context, vectorPreferences: VectorPreferences, activeSessionHolder: ActiveSessionHolder) {
         if (vectorPreferences.areNotificationEnabledForDevice()) {
             val activeSession = activeSessionHolder.getSafeActiveSession() ?: return
-
             when (vectorPreferences.getFdroidSyncBackgroundMode()) {
-                BackgroundSyncMode.FDROID_BACKGROUND_SYNC_MODE_FOR_BATTERY -> {
+                BackgroundSyncMode.FDROID_BACKGROUND_SYNC_MODE_FOR_BATTERY  -> {
                     // we rely on periodic worker
                     Timber.i("## Sync: Work scheduled to periodically sync in ${vectorPreferences.backgroundSyncDelay()}s")
                     activeSession.startAutomaticBackgroundSync(
@@ -42,7 +41,7 @@ object BackgroundSyncStarter {
                     AlarmSyncBroadcastReceiver.scheduleAlarm(context, activeSession.sessionId, vectorPreferences.backgroundSyncDelay())
                     Timber.i("## Sync: Alarm scheduled to start syncing")
                 }
-                BackgroundSyncMode.FDROID_BACKGROUND_SYNC_MODE_DISABLED -> {
+                BackgroundSyncMode.FDROID_BACKGROUND_SYNC_MODE_DISABLED     -> {
                     // we do nothing
                     Timber.i("## Sync: background sync is disabled")
                 }
diff --git a/vector/src/fdroid/java/im/vector/app/fdroid/service/FDroidGuardServiceStarter.kt b/vector/src/fdroid/java/im/vector/app/fdroid/service/FDroidGuardServiceStarter.kt
new file mode 100644
index 0000000000..d421c8bb87
--- /dev/null
+++ b/vector/src/fdroid/java/im/vector/app/fdroid/service/FDroidGuardServiceStarter.kt
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2021 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.app.fdroid.service
+
+import android.content.Context
+import android.content.Intent
+import androidx.core.content.ContextCompat
+import im.vector.app.core.services.GuardServiceStarter
+import im.vector.app.features.settings.VectorPreferences
+import timber.log.Timber
+import javax.inject.Inject
+
+class FDroidGuardServiceStarter @Inject constructor(
+        private val preferences: VectorPreferences,
+        private val appContext: Context
+) : GuardServiceStarter {
+
+    override fun start() {
+        if (preferences.isBackgroundSyncEnabled()) {
+            try {
+                Timber.i("## Sync: starting GuardService")
+                val intent = Intent(appContext, GuardService::class.java)
+                ContextCompat.startForegroundService(appContext, intent)
+            } catch (ex: Throwable) {
+                Timber.e("## Sync: ERROR starting GuardService")
+            }
+        }
+    }
+
+    override fun stop() {
+        val intent = Intent(appContext, GuardService::class.java)
+        appContext.stopService(intent)
+    }
+}
diff --git a/vector/src/fdroid/java/im/vector/app/fdroid/service/GuardService.kt b/vector/src/fdroid/java/im/vector/app/fdroid/service/GuardService.kt
new file mode 100644
index 0000000000..053cf87c17
--- /dev/null
+++ b/vector/src/fdroid/java/im/vector/app/fdroid/service/GuardService.kt
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2021 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package im.vector.app.fdroid.service
+
+import android.content.Intent
+import dagger.hilt.android.AndroidEntryPoint
+import im.vector.app.R
+import im.vector.app.core.services.VectorService
+import im.vector.app.features.notifications.NotificationUtils
+import javax.inject.Inject
+
+/**
+ * This no-op foreground service acts as a deterrent to the system eagerly killing the app process.
+ *
+ * Keeping the app process alive avoids some OEMs ignoring scheduled WorkManager and AlarmManager tasks
+ * when the app is not in the foreground.
+ */
+@AndroidEntryPoint
+class GuardService : VectorService() {
+
+    @Inject lateinit var notificationUtils: NotificationUtils
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        val notificationSubtitleRes = R.string.notification_listening_for_notifications
+        val notification = notificationUtils.buildForegroundServiceNotification(notificationSubtitleRes, false)
+        startForeground(NotificationUtils.NOTIFICATION_ID_FOREGROUND_SERVICE, notification)
+        return START_STICKY
+    }
+}
diff --git a/vector/src/gplay/java/im/vector/app/di/FlavorModule.kt b/vector/src/gplay/java/im/vector/app/di/FlavorModule.kt
new file mode 100644
index 0000000000..61fd476c87
--- /dev/null
+++ b/vector/src/gplay/java/im/vector/app/di/FlavorModule.kt
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.app.di
+
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+import im.vector.app.core.services.GuardServiceStarter
+
+@InstallIn(SingletonComponent::class)
+@Module
+abstract class FlavorModule {
+
+    companion object {
+
+        @Provides
+        @JvmStatic
+        fun provideGuardServiceStarter(): GuardServiceStarter {
+            return object : GuardServiceStarter {}
+        }
+    }
+}
diff --git a/vector/src/gplay/java/im/vector/app/push/fcm/FcmHelper.kt b/vector/src/gplay/java/im/vector/app/push/fcm/FcmHelper.kt
index fe091ffda3..52ad4be087 100755
--- a/vector/src/gplay/java/im/vector/app/push/fcm/FcmHelper.kt
+++ b/vector/src/gplay/java/im/vector/app/push/fcm/FcmHelper.kt
@@ -108,6 +108,6 @@ object FcmHelper {
 
     @Suppress("UNUSED_PARAMETER")
     fun onEnterBackground(context: Context, vectorPreferences: VectorPreferences, activeSessionHolder: ActiveSessionHolder) {
-        // TODO FCM fallback
+        // No op
     }
 }
diff --git a/vector/src/main/java/im/vector/app/core/di/ActiveSessionHolder.kt b/vector/src/main/java/im/vector/app/core/di/ActiveSessionHolder.kt
index e739cac95f..6b7b5f7f62 100644
--- a/vector/src/main/java/im/vector/app/core/di/ActiveSessionHolder.kt
+++ b/vector/src/main/java/im/vector/app/core/di/ActiveSessionHolder.kt
@@ -18,6 +18,7 @@ package im.vector.app.core.di
 
 import arrow.core.Option
 import im.vector.app.ActiveSessionDataSource
+import im.vector.app.core.services.GuardServiceStarter
 import im.vector.app.features.call.webrtc.WebRtcCallManager
 import im.vector.app.features.crypto.keysrequest.KeyRequestHandler
 import im.vector.app.features.crypto.verification.IncomingVerificationRequestHandler
@@ -36,7 +37,8 @@ class ActiveSessionHolder @Inject constructor(private val sessionObservableStore
                                               private val callManager: WebRtcCallManager,
                                               private val pushRuleTriggerListener: PushRuleTriggerListener,
                                               private val sessionListener: SessionListener,
-                                              private val imageManager: ImageManager
+                                              private val imageManager: ImageManager,
+                                              private val guardServiceStarter: GuardServiceStarter
 ) {
 
     private var activeSession: AtomicReference<Session?> = AtomicReference()
@@ -52,6 +54,7 @@ class ActiveSessionHolder @Inject constructor(private val sessionObservableStore
         pushRuleTriggerListener.startWithSession(session)
         session.callSignalingService().addCallListener(callManager)
         imageManager.onSessionStarted(session)
+        guardServiceStarter.start()
     }
 
     fun clearActiveSession() {
diff --git a/vector/src/main/java/im/vector/app/core/services/GuardServiceStarter.kt b/vector/src/main/java/im/vector/app/core/services/GuardServiceStarter.kt
new file mode 100644
index 0000000000..71c6816cea
--- /dev/null
+++ b/vector/src/main/java/im/vector/app/core/services/GuardServiceStarter.kt
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2021 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.app.core.services
+
+interface GuardServiceStarter {
+    fun start() {}
+    fun stop() {}
+}
diff --git a/vector/src/main/java/im/vector/app/core/services/VectorSyncService.kt b/vector/src/main/java/im/vector/app/core/services/VectorSyncService.kt
index 1fd86cac4d..08db8227a6 100644
--- a/vector/src/main/java/im/vector/app/core/services/VectorSyncService.kt
+++ b/vector/src/main/java/im/vector/app/core/services/VectorSyncService.kt
@@ -83,7 +83,7 @@ class VectorSyncService : SyncService() {
         val notificationSubtitleRes = if (isInitialSync) {
             R.string.notification_initial_sync
         } else {
-            R.string.notification_listening_for_events
+            R.string.notification_listening_for_notifications
         }
         val notification = notificationUtils.buildForegroundServiceNotification(notificationSubtitleRes, false)
         startForeground(NotificationUtils.NOTIFICATION_ID_FOREGROUND_SERVICE, notification)
diff --git a/vector/src/main/java/im/vector/app/features/settings/notifications/VectorSettingsNotificationPreferenceFragment.kt b/vector/src/main/java/im/vector/app/features/settings/notifications/VectorSettingsNotificationPreferenceFragment.kt
index b014b3d2dc..4199bd1753 100644
--- a/vector/src/main/java/im/vector/app/features/settings/notifications/VectorSettingsNotificationPreferenceFragment.kt
+++ b/vector/src/main/java/im/vector/app/features/settings/notifications/VectorSettingsNotificationPreferenceFragment.kt
@@ -37,6 +37,7 @@ import im.vector.app.core.preference.VectorPreference
 import im.vector.app.core.preference.VectorPreferenceCategory
 import im.vector.app.core.preference.VectorSwitchPreference
 import im.vector.app.core.pushers.PushersManager
+import im.vector.app.core.services.GuardServiceStarter
 import im.vector.app.core.utils.isIgnoringBatteryOptimizations
 import im.vector.app.core.utils.requestDisablingBatteryOptimization
 import im.vector.app.features.notifications.NotificationUtils
@@ -61,7 +62,8 @@ import javax.inject.Inject
 class VectorSettingsNotificationPreferenceFragment @Inject constructor(
         private val pushManager: PushersManager,
         private val activeSessionHolder: ActiveSessionHolder,
-        private val vectorPreferences: VectorPreferences
+        private val vectorPreferences: VectorPreferences,
+        private val guardServiceStarter: GuardServiceStarter
 ) : VectorSettingsBaseFragment(),
         BackgroundSyncModeChooserDialog.InteractionListener {
 
@@ -216,14 +218,19 @@ class VectorSettingsNotificationPreferenceFragment @Inject constructor(
             it.isVisible = !FcmHelper.isPushSupported()
         }
 
+        val backgroundSyncEnabled = vectorPreferences.isBackgroundSyncEnabled()
         findPreference<VectorEditTextPreference>(VectorPreferences.SETTINGS_SET_SYNC_TIMEOUT_PREFERENCE_KEY)?.let {
-            it.isEnabled = vectorPreferences.isBackgroundSyncEnabled()
+            it.isEnabled = backgroundSyncEnabled
             it.summary = secondsToText(vectorPreferences.backgroundSyncTimeOut())
         }
         findPreference<VectorEditTextPreference>(VectorPreferences.SETTINGS_SET_SYNC_DELAY_PREFERENCE_KEY)?.let {
-            it.isEnabled = vectorPreferences.isBackgroundSyncEnabled()
+            it.isEnabled = backgroundSyncEnabled
             it.summary = secondsToText(vectorPreferences.backgroundSyncDelay())
         }
+        when {
+            backgroundSyncEnabled -> guardServiceStarter.start()
+            else                  -> guardServiceStarter.stop()
+        }
     }
 
     /**
diff --git a/vector/src/main/res/values/strings.xml b/vector/src/main/res/values/strings.xml
index 0e8197dbae..d345971962 100644
--- a/vector/src/main/res/values/strings.xml
+++ b/vector/src/main/res/values/strings.xml
@@ -322,6 +322,7 @@
     <string name="notification_sync_init">Initializing service</string>
     <string name="notification_sync_in_progress">Synchronising…</string>
     <string name="notification_listening_for_events">Listening for events</string>
+    <string name="notification_listening_for_notifications">Listening for notifications</string>
     <string name="notification_noisy_notifications">Noisy notifications</string>
     <string name="notification_silent_notifications">Silent notifications</string>