[xmpp-enjoyer]

For those who still like the classic style of messengers, Psi [1] offers an old-school, extremely customisable interface, and is still actively maintained. It integrates nicely with all the desktop platforms as well.

[1] https://psi-im.org/

[Semaphor]

Kinda. The normal version hasn’t seen a release in 4 years, only the experimental psi+ version is maintained, and it is unclear which features it actually supports as all (at least in the wiki in English) information is heavily outdated.