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).


You also don’t need to do this on Android unless you are concerned about random people seeing the messages on your screen. Signal on Android does not use Google’s push notification service
You most certainly do. I looked in my notification history in my founding of signal messages.
Then I turned off my notification history.
as far as i know signal uses Google’s notification service and if you want it to not you need to use Molly