So here's the thing, every time I try to move away from Facebook messenger I run into the same problem, nobody else in my friends or family actually want to use a secure, private messenger app like signal or telegram, my wife, my parents, my in-laws, my friends they're ALL on Facebook and they will never take signal seriously enough to actually use it, it really bums me out that there are these far superior options but without anyone else using them they're pointless..
Anyway what apps do you use to stay in touch with people?
I am. My good friend created telegram client using only their protocol documentation and I've been following his with very closely, and I have to say their E2E encryption is very very good. Only thing I noticed is they are using some non-standard mode of symmetric block cipher to make it stream cipher, after keys have already been exchanged, but I failed to find weakness in it, and all encryption specialists I know of failed too. It's just consecutive application of two different modes, both of which are established to be good.
Currently my job involves working with tdlib, Telegram protocol client library written by Telegram themselves; though this job doesn't really focus on security.
I do know how to avoid detection of my communication with someone via MITM, and when appropriate we go use secret chats, which are E2E encrypted, and clean them up after a day.
Normal chats and groups are as secure as Telegram as a service is. This is true for every other messenger, without exceptions. You need security, you use E2E. And even then you are as secure as your phone, which is not much for all mobile operating systems.