I host Rocket.Chat for my wife’s business. The free self-hosted version now allows up to 50 users before having to purchase a license (was 25 prior to the version 7 update). If you kick a user you simply deactivate their account and regain the user slot. Rather than deleting a user completely which would additionally delete any messages they’ve posted.

Easy to host, easy to upgrade. Mobile apps both IOS and Android work well.

I wanted to use Zulip as I felt the interface was cleaner. But the 10 user limit was a deal breaker.

I use Jellyfin. You have to install the Bookshelf plugin (or at least I didn’t the time I set it up, may be a default now). Saves progress, and gives me one less service to manage as I use Jellyfin for Movies, TV, and Music libraries already.