Are you sure? At least with Kodi for specials like Futurama you make a Season 0 with them that the scrapers understand. Seems like Jellyfin understands that too: https://jellyfin.org/docs/general/server/media/shows

I guess for Theatrical TV show movies like The Simpsons Movie it might be more complicated, but worse case you always create or edit your own NFO files with something like MediaElch and have Jellyfin use those.

I think it's better to have genres in the NFO files and not in the folder structure. A show or movie can easily fall into two or genres which is not going to get captured by a single folder.