Let me throw another one on the mix, which I'd say fails the convenience test, for now at least. There is tox (https://tox.chat/) which seems to be promising.

Regarding signal, I tried and didn't find an explanation for why each of the many permissions is required. I guess I might need a tinfoil hat but apps that require lots of permissions always make me suspicious - mind you that I'm not implying signal is not secure or does nasty things.