Where can I download non-English dubs?

Nyaa. si has non english dubs of some show. The tags aren’t always accurate so it might say English translated and actually include English and other dubs/subs

IMHO you have to download the whole media again, only the dub is very difficult that would match the video seamlessly - even subs often desync because in that particular zone they cut 2 seconds from a scene or they are playing the media at a wrong frame rate (now less common but with analog media it happened a lot)

Depends on the language and the content itself. I'm hunting one where all the torrents are from 2012, so... Gave up, and buying the actual media. 😂

What kind of media? I'm assuming live action films originally in English, but maybe you're talking about serialised TV shows, animated series, games, or something else?

Depending on the type of media, the answers may vary a lot.