I'm looking for an open-source XMPP client that
- works on Linux, but also other systems,
- has native OTR support (doesn't require plugins)
- and of course, has a nice UI.
I have used Tor Messenger and it was the best client I have used so far. Nice design, OTR support, cross-platform. However the latest version is seriously bugged.
Pidgin has no OTR support and to be honest, awful UI. Same goes with Instantbird (even though Tor Messenger is based on it, the native UI is awful and lacks OTR support).
Edit: Pidgin might be the best option, the OTR plugin is made by the same people who made OTR and it has a good plugin support in general. The UI is something I will have to get used to.