I have been working on getting Signal woven into my Messaging app all weekend and it’s come together really nicely so far. I started the easy route, hosting signal-cli on my home server like @lisa is describing below, but I’m tinkering on getting it set up to host on the phone itself…stay tuned. I’ve got it integrated into a Desktop Sync webapp as well–it’s fun 
Admittedly I don’t use beeper or whatsapp so I don’t see myself implementing those.