There are a lot of communities that were created in the last week but never had any kind of interaction or their mods never started to post to attract people (they don’t even have rules or a description).
Will there be some kind of cleanup or will it stay there until someone asks to take over it?
Nope I think you misunderstood. OP is asking about inactive communities on lemmy.fmhy.ml itself, inactive communities on another instance has no impact here. You are welcome to create your own single user instance, it’s infact encouraged in fediverse to balance the load.
Oh that makes so much more sense. Thank you for your help!