IETF Standards don't get a large marketing budget assigned to them like many other messengers have, but there are quite a few community projects which are actively developed. Off the top of my head there is Conversations on Android (gratis when you get it from F-Droid), Monal on iOS, Gajim on the desktop, Dino, Movim, Profanity, converse.js, Prosody, ejabberd, ...