I run my own instance and I have created some communities that I loved back on Reddit. I searched and no similar communities seem to exist in the fedeverse yet. Obviously there is nobody visiting them right now, so how would you go about trying to promote it to attract some discussion?
Honestly just create them, and don't leave them for dead (give them content). That way they show up in searches on peoples instances and places like https://browse.feddit.de/