I have a lot pushed in Silence direction for SMS (here, there, and in this forum too), but I feel they don’t have resource to integrate Silence Protocol into the SMS app, which is too bad.
About messaging app, I have discovered Jami on F-Droid : this is really promising ! I don’t know why it is not known so much, I have tested and it works pretty well so far. It’s a messaging app like Signal, but without server (so same method as Silence) and you can send messages, call, but also video call. Everything is store in local (because serverless), and is peer-to-peer encrypted.