Add the metadata yourself on TMDB, get it approved (usually happens by itself) and then identify the entry in JF.
That's how I did it for https://www.themoviedb.org/tv/215216-bigger-better-baden-wurttemberg/
Edit: Upside: You help the community (mirrored to sites like trakt) and others can benefit from your work as you do from others work (metadata providers, jellyfin).