Somehow any time I hear Matrix I get instant unpleasant taste in my mouth. I know that you have a private community but the amount of censorship in the other public matrix groups is on another level.
Element Server Suite, on the Matrix Network.
Until Nostr is ready and capable for these use-cases, it'll be our go to, and has been for the past 4 years since we moved our Gaming community off Discord and family off other chat apps.
Hosting a server is super easy now, and in just a year it's night and day compared to just a year ago as they nail in the spec for Matrix 2.0 - https://github.com/element-hq/ess-helm
We federate with other Matrix servers and communities.