Stoat is an open-source Discord alternative with no central server structure. Basically, it's a Discord-esque chat network not owned by Discord, the scummiest company that I've ever interacted with. IIRC, it'sdecentralized enough that Discord can't sue them out of business.

Kisscourse is a Hackhub discussion server on Stoat for the community to use. You can find Kisscourse via the following invite link: https://stt.gg/baajZppp