Do you have the logs for the crash report?
Do you have sandboxed Play Services installed by any chance?
Have you tried backing up your chats, uninstalling Signal, restarting the device, downloading the APK, and installing the Signal APK (assuming that that's your original preferred method)?
Set battery optimization to unrestricted from the system settings and allow installation from unknown sources for the app. Import your backup during the initial launch of the app's setup wizard.
Edit: Please see https://github.com/signalapp/Signal-Android/issues/13252 is that exactly the same thing as you are experiencing?
Edit 2: https://github.com/signalapp/Signal-Android/issues/13261
Edit 3: https://github.com/signalapp/Signal-Android/commit/750825b3c36a6f38b15067dae1ba237f2a427e1b