I've spoken before about how much I like Zulip. I don't know if it's any more stable or available than Slack, but I do like that the fundamental concepts expose

I've spoken before about how much I like Zulip. I don't know if it's any more stable or available than Slack, but I do like that the fundamental concepts exposed by Zulip actually encourage focused, productive conversation (something that always feels like a losing battle in Slack).