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.
Please share a github link to the private communities feature.
But it is possible to have a private instance were the instance cannot have contact to the federation or only allow selected users from the federation to view the instance?
Yes. Simply have the following in your configuration JSON file:
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.
You can search for it on the github issues.