I can recommend Zulip. In one of the instances I'm on, we have a rule that "topics outside of #random are treated like email". People are supposed to post multi

I can recommend Zulip. In one of the instances I'm on, we have a rule that "topics outside of #random are treated like email". People are supposed to post multi-paragraph posts that go into detail, and replies are similarly long and quote all relevant parts. I love that mode of communication, it feels less like drive-by opinion-slinging and more like conversation.