We have a discord server that we are slowly migrating into a federated and self-hosted IRC and Galene setup. IRC because it's easy to setup both servers and clients, Galene is a voice/video chat system that can be self-hosted and is comparatively lightweight and can do a few things you can't easily do with discord. (Share multiple windows from the same or different computers for example). We also tried with jitsi meet before, which works, but is more resource intensive to self-host. I experimented with maptool a bit but it doesn't really fit my playstyle. We generally don't use vtts.

I used to stick with Discord for most of my group gaming until they changed a bunch of policies and the overall vibe shifted. Now, I'm mostly on Matrix for chat and dice bots and sometimes set up Jitsi if we need voice. The flexibility is nice and feels less corporate, like you said. IRC is solid if you don't mind something simple, and I've even tried hosting with Galene, which isn’t too tough once you get the basics down.