One thing, in the threadiverse it’s generally called a community rather than a “sublemmy”, the urls use /c/.

Though unfortunately I’m not aware of a specific community to request communities, usually the answer around here is “be the change you want to see”, if you want one, try making/running one, maybe it’ll catch on 🤷.

One thing though is its going to be difficult to host something like that on any instance and it remain neutral lol.