Could lemmy be used as a private self hosted forum?
And could lemmy be used as a private forum were only registered users and whitelisted users can view, post and comment on the instance. This way you can have a private instance which only paid users of your group or club can join like many membership website forums have.
Is it possible to not have your instance federated but allow a whitelist of users to access the instsnce from outside the instance?
You can allow/block access by instance, but not by user.