Broadcast Receivers not working in background in android oreo and pie

seems to work fine Your app's target API level is 23, that is android M (6.0). In android M there are huge changes related to user-permissions. Here is nice article explaining the changes.

I hope this helps . android.intent.action.BOOT_COMPLETED and android.intent.action.TIME_SET are on the whitelist that you linked to. Those broadcasts should work as it always has.
android.intent.action.MY_PACKAGE_REPLACED is not an implicit broadcast. It will be "broadcast" only to your app, via an explicit Intent. This should work as it always has.

I hope this helps you . Once your MainActivity is destroyed, your BroadcastReceiver goes away. This will occur:
If the user presses BACK, or If the user navigates away by some other means (e.g., presses HOME) and your process is terminated

Hope this helps Pasting the line from android official documentation

I wish this helpful for you Broadcast Limitations
If an app registers to receive broadcasts, the app's receiver consumes resources every time the broadcast is sent. This can cause problems if too many apps register to receive broadcasts based on system events; a system event that triggers a broadcast can cause all of those apps to consume resources in rapid succession, impairing the user experience. To mitigate this problem, Android 7.0 (API level 25) placed limitations on broadcasts, as described in Background Optimization. Android 8.0 (API level 26) makes these limitations more stringent.