How to prevent metadata from bad TVDB matching

[Renoir]

1.  Not that I am aware of.
2.  That setting would use the embedded title instead of the file name when constructing the query for TMDB/TVDB, etc.  It does not configure Jellyfin to only use the embedded metadata.
3.  If you set TMDB as the primary, any TVDB mismatch SHOULDN'T be a problem.  However, if your metadata provider order of precedence is not consistent through each metadata category, that could cause problems if TMDB and TVDB match on different shows.

If you need only local metadata for a show, you have to disable all providers in the library for each category, scan in the show, lock the metadata for the show, then re-enable the online providers for future shows.

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theguymadmax also has a good suggestion.  Using the ID in the folder name should correctly map the show, even between providers.  Assuming it exists in both locations.

Thanks for your comprehensive reply. 

1. Bummer.
   
2. Ah! <lightbulb>
   
3. I re-tested after making the search order identical for all data categories. JF still picked up additional data from TVDB for a different series (and, most annoying, lots of cast entries). That's even the case with a [tmdb-xxxxx] tag in the series folder name. Perhaps a special code like [tvdbid-0] could force JF to not try to match against a specific provider, for a specific series. (Enhancement?) 
   
4. Per your final advice, I disabled all online providers, leaving only the Embedded episode image extractor, but now JF is not picking up episode numbers and episodes are listed alphabetically by title rather than in sequence. 
   
5. Also, JF does not then extract episode descriptions. Isn't that what the library option Prefer embedded episode information over filenames does?