I think they mean like IRC, Matrix, or Discord: real-time chat rather than asynchronous. They may mean such a thing integrated into a Lemmy client, but it's pretty unclear in the original question.
That's less about the app and more about the community I would say. I get into those kinds of discussions on freenode (irc) but also on some old school web forums. I'm not hip enough for Matrix but I guess it has some users too.