So to summarize jmp.chat virtual phone numbers can now be used (SMS only, no voice) from matrix! nice one
It is really just the aria-net.org Bifrost bridge. You could have probably done that before.
Yes, in fact some people were doing it before. The only change is that we have made it easier to do from signup flow, provided a tool at https://cheogram.com/matrix for people to get the mxids for their phone numbers, and updated some of our docs to be more accessible to matrix users.
Extensible Messaging and Presence Protocol (XMPP) is a communication protocol for message-oriented middleware based on XML. Learn more about it here.
Dedicated Lemmy instance
XMPP.net Provider List
Also see JoinJabber.org FAQ