Is this eligible? https://meta.wikimedia.org/wiki/Requests_for_new_languages/Wikipedia_East_Franconian_German

My personal opinion is No, but that's just because I hate all German dialects except my own.
Jokes aside, let's consider whether there is a valid ISO code, and whether the language is "sufficiently unique that it could not coexist on a more general wiki. In most cases, this excludes regional dialects and different written forms of the same language." (per Language proposal policy).

There is a valid ISO 639-3 code, vmf, but there seems to be some confusion as to what this code comprehends (see the Request on Meta).

Cf. also on Incubator the category for the different dialects in which they write articles there: <https://incubator.wikimedia.org/wiki/Category:Wp/vmf/Adigl_nach_Dial%C3%A4gd>

I don't think there could be a more general wiki, however the exact definition of which dialects this wiki (vmf) should cover might be controversial.