Curious, what didn’t you like about Matrix specifically? I’m in the process of evaluating it for my friends. With the Element client, so far it seems pretty dang similar? Space = server, room = channel, there are also access controls. Seems like there’s voice and video chats too.

https://matrix.org/try-matrix/ With the Element client, it’s a pretty close experience to Slack/Discord.

If you want access to some underlying knobs and buttons, but without running your own email server, then Migadu might be interesting.