Communities in Lemmy/Mbin are not federated by default. So when you create a new community, it will only be available to your instance. At least 1 person from all other instances must follow it in order to make it available. This tool does that. It follows your community from all remote instances until at least 1 other person follows it.
Someone has to ask the admins to enable those, I remember there was some concern with resource consumption some time back.
Dubvee.org too
FYI @[email protected]