This is a great list of tips for improving your Signal privacy from @yaelwrites.
I found this part especially meaningful:
“Turning off biometrics makes it annoying to use your phone…If that’s you, remember that both Android and iOS have a quick lockout that forces a passcode and disables biometrics until you re-enter it: on iPhone, hold the side + volume button until the power-off screen appears, then cancel; on most Androids, hold power and tap Lockdown.”
https://blog.yaelwrites.com/how-to-keep-the-feds-out-of-your-signal-messages