Currently https://cheogram.com/ (an advanced Conversations fork)

But the new Conversations 3.0 UI overhaul should be released soon.

Honourable mention for a great looking work in progress: https://moxxy.org/ (not suitable as a daily driver yet)

I second the vote for cheogram. As for the pending conversations ui overhaul, of which I know nothing, that should automatically transfer over to cheogram once it goes public. Cheogram extends conversations, wndci don't think they changed ui code.

c0nnect and c0nnect pro

I think actually is monocles chat