Since I wrote this, many have introduced me to movim, and it's pretty slick! I'm still experimenting, but I like a lot of what I see. Still missing moderation tools for groups, though.
Let me add that I am keenly aware of the cryptographic issues you are about to bring up about any of these options. I read and deeply respect the work of @soatok and others, and understand the concerns around OMEMO for XMPP, Matrix, etc.
Security is a balance between risk and value. I cannot decide for you what the right balance is, but I know from hard-won experience that building a community is about more than "perfect" security.
@mttaggart I have a voice chat plugin for Discourse, recently shared at https://meta.discourse.org/t/resenha-add-discord-style-voice-rooms-to-your-community/389056
The web nowadays is super powerful, we can cover a lot of Discord use cases with open tech.
That voice chat is also p2p and encrypted by the nature of WebRTC.

Hey everyone! Sharing Resenha, an experimental plugin that adds voice chat rooms directly into Discourse — no external apps, no media servers, just peer-to-peer voice in your sidebar. Try It Live 👉 https://discourse-on-a-pi5.falco.dev/ (Yes, it runs on a Raspberry Pi 5 — that’s how lightweight this is.) How It Works Click a room in the sidebar to join, click again to leave. All audio goes peer-to-peer via WebRTC — your Discourse server only handles signaling, never media. A defa...