Jupyter considering leaving @matrix in favor of Slack, Discord, or @zulip https://github.com/jupyterlab/team-compass/issues/213
I was a big fan of Matrix after I discovered it from @Cadair for @OpenAstronomy , but it's true that it has weird UX issues, its behavior is erratic (very often I would see "all messages are encrypted" and had no idea how to fix it), the official clients have been moving slowly, their spec is super complex, bridges were unstable, moderation was hard...
Still better than IRC, but that's not much.