XMPP - Free, private with OMEMO enabled, decentralized, voice, vid. A little less user-friendly / janky.
IRC - well, doesn't have a lot of features, no voice or video, but a lot of the communities I visit that also have an IRC are typically focused and interesting at least ("tight knit"). Free, decentralized. History is most searchable / backup-able probably.
@foxxy . What is a good platform and how do you look up chat rooms and stuff of interest