TLDR: signal content in Apple notification can be retrieved even after signal app deletion.
I saw from this reddit thread: Signal messages retrieved from iPhone after uninstalling app. : signal
Referencing this news article: Pretti Killing May Affect ICE Prairieland “Antifa Cell” Terrorism Trial
The mention of signal is in court documents here: March 10: Federal Trial Day 12 - Support the Prairieland Defendants
Signal chat evidence from Sharp’s device (Exhibit 158):
Messages were recovered from Sharp’s phone through Apple’s internal notification storage — Signal had been removed, but incoming notifications were preserved in internal memory. Only incoming messages were captured (no outgoing).
It’s worth noting apps can avoid this on Android: https://tuta.com/blog/google-push-alternative#alternatives-to-google-push
Any FDroid app cannot use Firebase for push notifications since it’s proprietary: https://forum.f-droid.org/t/firebase-allowed-in-fdroid-apps/7540
It’s not because of push notifications. the message is not sent to firebase, just a signal that the app should do a refresh.
It’s because the system saves the notifications apps posted to the notification menu.
but yes. don’t use firebase push notifications if you can avoid it. use a unifiedpush based system. base signal app does not support it, only molly. there are some difficulties though with that that are unique to signal.