I don’t know much about them to be honest, these were just the apps people were talking about

https://play.google.com/store/apps/details?id=com.google.android.safetycore

https://play.google.com/store/apps/details?id=com.google.android.contactkeys

I think Nim is the frontrunner here. Close to Python to write because it is so expressive, close to C speed because it is compiled properly.

There’s also URLCheck:

https://f-droid.org/packages/com.trianguloy.urlchecker

https://www.archivebuttons.com/ is the way

Matrix is very good and flexible. If you need something that is interface-compatible with Discord, there is: https://revolt.chat/