While videos can be individually tagged as dubbed, the information is already included within themoviedb.org data set in the “Original Language” field.
It strikes me that this tagging could be done automatically when importing the item?
Specifically for spanish, as long as the tmdb page “original language” field includes Español, Castellano, or Spanish it would be automatically tagged as “Native” even if other languages are listed. And if it doesn’t, then it would be tagged as “Dubbed”.
If we want to get fancy, if the field includes both Spanish and anything else, it would receive an additional tag of “Multiple Languages” (but that is less important).
Better still to have a toggle on the video browsing page akin to “Item Type” that can be toggled “Native” or “Dubbed”.
This would simplify people’s searches regardless of where they are in their learning process, helping people looking for dubbed content they are already familiar with as well as people looking for native content they don’t yet know exists.