Yep, time to self host one of the awesome self hosting list's chat options. This will teach independence too. I have a ready ansible deployment for zulip using docker in my repos [1], publicly available. All that's needed is a server, setting some variables in ansible, deploying that thing, and adding backups. It will cost significantly less than any slack subscription and will not cost per user.
[1]: https://codeberg.org/ZelphirKaltstahl/server-management/src/...