But after using it a while I now really dislike Slack et al, both in professional teams and for open source communities.
Zulip can give you the best of both worlds. It's a regular chat. But the threading model also encourages long-form, more forum or email like discussions.
Threads are easily discoverable and it's trivial to catch up on all the relevant discussions that you missed, while skipping everything that doesn't concern you.
You can still have some regular chat channels for typical ephemeral discussion that no-one is expected to read. It's really a great tool.
The only downside is the very subpar UX when compared to Discord or even Slack.