I'm sorry about it. I think that was a misunderstanding. Flag on tv series was not possible right? On the demo you can see no https://dooplay.themes.pe/tvshows/
Has someone already built filter into its theme?
I tryed this one
https://de.wordpress.org/plugins/beautiful-taxonomy-filters/
I put it into archive.php to filter for language/region
Looks not perfect but it works
do someone use another plugin?