I know there are multiple answers to these questions, I tried them all which were suggested in other StackOverflow posts, such as
- Using FlagImmutable, I changed all of the flags of PendingIntents
- used the work-manager library in my app module, the stable one
- Updated FireBase But still, application crashes in Android 12 and I get the following error: Targeting S+ (version 31 and above) requires that one of FLAG_IMMUTABLE or FLAG_MUTABLE be specified when creating a PendingIntent.