Maybe it has no hobby community due to thinking that it is owned by the corporate realm. That may be true for SIP (voice/SMS) but beyond that anybody can run it and I don't see why there can't be a robust grass-roots data-only network. I don't know much but maybe will start looking at it more and can start something on nostr.
Discussion
Until recently I had my own voip network and pbx with desktop/landline phones because I'm a nerd.