FRIENDICA seems to me to be the future, a truly federated social platform, - a Diaspora done right - and the recently started Red gives the ability for the first time to migrate your account from one federated server to the next!
BUT if you want to use it as a forum (and not just as a social-media platform), the learning curve is very steep.Someone has to devote his time to understand how a "forum" works (ala Facebook "Pages"), then he should create a "forum", and share the usage-knowledge with the rest, so as to save their time.
In particular, in Friendica there are no "pages" notion.
Instead, there are
- multiple "Profiles" per account and
- multiple "Accounts" linked together (called "Managed Accounts"), when these accounts share common Passwords and Emails.
Fora (or a fb "page"), counter-intuitively, DO NOT correspond to "profiles", but to "Managed Accounts"!
So, someone has to add a new "Managed Account" acting as the "forum" and the members should apply for "friendship", similar to FB.
Then, the owner of that "Managed Account" can either:
- share the password to the Admins of the forum,or
- add those "friends" willing to administer as "Managers".
There are many test-servers to try those steps, i.e. https://tryfriendica.net/