Ask HN: There should be a peer-to-peer chat program by default on any OS

I've just run through the list of ways to get my team on video conference chat and man was that a pain... Went from MS Teams to Hangouts and still not there yet. Any suggestions? I want ad-hoc, pref p2p and do wish it were installed by default on every os or is something p2p I can install now? Mac mainly but Windows boxes too.