When you say threads do you mean within a chatroom or something like an Elements/Discord structure with "channel" and "subchannel" because for the former there are decent options, but for the latter there is a lack of "spaces" being defined but it is in development by the Movim and Slidge devs. I went pretty far down this rabbit hole and ended on Zulip being the easiest FOSS drop-in for Discord that wasn't Matrix, though people who manage to run it tend to love MatterMost.
Cooper8
joined 4 hours ago
OK, you might be on to something there.
Gajim is the favorite for threads https://gajim.org/