I just like it and I value my privacy. I don’t try to convince anyone. I explain it is both a hobby and a kind of political statement.

You have a very restrictive definition of a smartphone. Sideloading is a natural way for installing apps. In fact it has for a very long time been the only way to install apps on a Windows computer.

Self-hosting for a bit less than 10 years. My main pain is that my setup is now stable and I have nothing left to tinker with.

Look at https://github.com/coturn/coturn

Your own xmpp server

They should support GrapheneOS rather than try and make something “more free” from LineageOS.

Right, but how many people are willing to use Signal? I have my own messaging server, and those who don’t want to use it write sms to me.

I have self-hosted Matrix for a couple of years. I eventually settled with xmpp/ejabberd/conversations. It is easier to maintain and less resource intensive, especially if you want to go the federation route.