A post in the Cardano forum alerted me to the existence of this Matrix community, centered around Cardano.

I’ll put a link in the sidebar, as I feel that this Matrix room is one of the only instances of FOSS technologies being used for community discussion in the Cardano ecosystem besides this one.

It kind of blows my mind how dependent on centralized, closed-source technologies a community centered around a decentralized, open source technology is.