In response to your postscript: You can search here for other communities: https://browse.feddit.de and there may be other search, please let me know if you find them. That one is a bit slow to update. I used that to determine that there was no community yet for a topic. So I tried to get a feel for which lemmy might be best for it and created it there. The one I created was Trader Joe's Unofficial You can see I even added a note in the description about it being my first and trying to add a better/more mod.
TL;DR See if your community interest already exists anywhere, and if not, go create it!
I'm having trouble finding communities in lemmy.ml here (is one of the unblocked instances). I can find them from another lemmy instance, just not here. How often are the communities updated? I'm hoping to make beehaw my 'home' instance.