There's also open-source solutions such as rocket.chat, Mattermost, and likely a few more I haven't played with.
I wish Mattermost wasn't always trying to nudge you out of community version, but otherwise pretty solid, better than Slack IMO. Is unfortunate they require weird gitlab spoof bypass to use SSO in community version. Shameful it's not out of the box.
Many years ago Pidgin with multi-channel IRC was all I needed, but seems Slack killed that whole party, which brings us to the current situation :(.
I wish Mattermost wasn't always trying to nudge you out of community version, but otherwise pretty solid, better than Slack IMO. Is unfortunate they require weird gitlab spoof bypass to use SSO in community version. Shameful it's not out of the box.
Many years ago Pidgin with multi-channel IRC was all I needed, but seems Slack killed that whole party, which brings us to the current situation :(.