Strongly suggest Molly for Signal:

https://github.com/mollyim/mollyim-android?tab=readme-ov-file#features

Hardened fork with message DB encrypted with a passphrase, RAM wiper, inbuilt Orbot Tor proxy support and supporting multiple devices including ones without phone numbers and much more.

If you're compromised to that level, they could read your notification contents. Change in the options not to show any. If they can record the screen you're finished regardless. Apps are only as secure as the OS running on them and this is why you use a hardened OS.