Android: F-Droid edition of Conversations/Cheogram is free, unlike that of the Play Store (Google charges rent), though they’re identical.
Browser, adds social network layer that any XMPP account can access: https://movim.eu/
iOS, MacOS: https://monal-im.org/
Linux, Windows: https://gajim.org/download/
Bridge XMPP with inferior platforms: https://github.com/42wim/matterbridge
Monocles Chat Android, Gajim MacOS, & things of that nature are likely fine too, can’t vouch personally. I’d be happy to explain why Matrix sucks, if “Electron client” + “National Endowment for Democracy-funded” won’t suffice.