On Linux, I really like Dino, because it's one of the few clients that played nice with OMEMO. I use XMPP on my PC and on my phone and that seemed to trip some clients up.

I also liked Gajim on Windows for much the same reasons, but this was years ago, I imagine it's pretty good now, too.

Gajim. It's still developed.

Gajim on desktop (love the new ui specially workspaces) and monocles (fork of conversations) on mobile. works great for me and apart of my servers hiccups every now and then as far as the clients go, I have no problems with encryption nor voip calls on the phone.

• terminal: profanity (really cool, it became what I regularly use, no audio/video calls though in which case a gui like dino can be used, syncing between the two)
• gui: dino (there's a fork called dinox)
• android: conversations (from f-droid)

I use and prefer Gajim but I would install the Flatpak version if possible, especially on Ubuntu/Debian or derivatives, because the one in the apt repository (at least for Ubuntu 24.04) is super old and never seems to get updated, and there have been several bug fixes.

Cheogram for Android and Dino for Linux.

Miranda-NG was great, but it's Windows only and I have no idea how it supports latest XMPP features and such. Haven't used XMPP on it for a while now..

Dino and Conversations. They work well and have a nice UI.