There's a bit of discontent with #FreePBX to the point that a fork has been discussed. https://community.freepbx.org/t/support-quality-cutting-corners/102101/3
The owner of the librepbx domains has not responded to my inquiry. I was investigating others and software that doesn't rely on Asterisk, and it's a little confusing. #Freeswitch and #Kamailio seem to be the primary competitors, and #Yate looks interesting.
I'd like to have a h.323 option because I think faxing may prefer that to t.38 which is poorly supported.