GNU Jami works beautifully most of the time these days, it's been the most reliable teleconferencing system I've used. group chats have been supported for a while, and they work pretty well. having the same account on multiple devices seems to help when the occasional device has trouble getting through due to network issues. I set up a single-user "group" chat to send myself reminders from one laptop to the other. it's been great to send files to other users without resorting to intermediaries.