I need to be dead honest here. This is Lemmy. If it isn't there, make it. I get not wanting to moderate etc. but if you want that thing to happen you're going to have to make it and you're going to have to post as often as you can. Do I want to mod a community? Not at all, but I've made two and I post to both as often as I can when the opportunity strikes.
The whole "this niche thing doesn't exist so I'm not enjoying Lemmy" argument falls flat for me. Just take the leap and keep going at the pace you can. Even if it is slow, it's something and people may migrate and enjoy the content. Ignore downvotes, they don't really matter here. Just post stuff, even if it is irregular.