First, I want to congratulate to team. This is a big and very good work and software
Second, sorry about my poor english 
I love Sonarr, but I have a problem, I´m spanish and work with two excellent trackers (HD-SPAIN and HDCITY).Names on torrents at this tracker can include “spanish_series_tittle” or if I have luck “spanish_series_tittle (english_series_tittle)”. Example “Juego de Tronos” (instead of “Game of Thrones”) or "El tirador (shooter).
Then I´m not able to download with sonnar aprox 50/60% of series.
Also, I have problems when tracker put a wrong name to series. Example “Mayans M.C”, Sonarr query to Jackett about “Mayans%20MC”, but HD-SPAIN have a torrent “Mayans M.C.” and HDCITY hace a torrent “Mayans M C”.
I understand that implement a multi-language search to TVDB it´s a hard work (I saw this request at 2014 I think that is abandoned). And, also, this not resolve second problem.
Because I want to propose a more simple workaround: Add a field to series named “Tracker title”. With this new field whe you query to indexers you could check if this field not is empty, and then to use it to bulid indexer query.
If is possible multi (comma separated) titles it would be perfect, then you could put diferent titles of same serie for differents trackers.
Maybe, if you could tell me where is code of edit serie gui, object for serie and build query for indexer I could help to evaluate how hard could be this change.
Many thanks at advance