Having used essentially all of these kinds of software (life as a freelancer, I think I had 8 different chat apps on my laptop at one point :/) I can genuinely say that Zulip combined with Jitsi Meet is the happy path (at least for me). I found MM quite clunky (although it's been about 2 years since I saw it in the wild) and Slack intolerable.
Weirdly, I actually didn't mind Teams too much, after you stop creating new conversations instead of replying (which took me WEEKS), it was reasonably stable and it just sort of worked for me. Although I hear a lot of people gripe about it.
Weirdly, I actually didn't mind Teams too much, after you stop creating new conversations instead of replying (which took me WEEKS), it was reasonably stable and it just sort of worked for me. Although I hear a lot of people gripe about it.