I get that some people leave if doors aren't open here. Can't you/someone add like a big banner with alternative instances where to register ?? 😅
I remember when i first joined i ended on mastodon.social as well before eventually moving because i didn't get how the federation worked.
But i'm pretty sure a banner saying "it's closed here, you can go there there or there" might help.
Anyway good luck with all those newcomers hope your servers will manage them 😉
Maybe add the instance picker from joinmastodon.org on your instance homepage?
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!