Zulip is so much better than Slack (topics not threads! so much better— and i am someone who cannot choose an e-mail subject to save my life), also better than IRC. Zulip is what we moved to.
Free software that you *can* self-host but also available as a service.
I think for many it will hit that sweet spot between convenience and freedom/control.
Though i don't want to derail the main thread too much, which is that IRC is alive and well.
`irc.indymedia.org` is where @mayfirst and some other groups we are part of are on, everything else is on `libera.chat` i think.