It's technically challenging; 1:1 calls can use WebRTC without a server (after 'signaling'), whereas a good experience with a group call usually requires a serv

It's technically challenging; 1:1 calls can use WebRTC without a server (after 'signaling'), whereas a good experience with a group call usually requires a server to mix audio and video. It's difficult to do that when it's encrypted. The only group I'm aware of that are taking a serious look at it is the Matrix team. If you see it anywhere, it'll likely be on that protocol first.