You can find subtitles online separately, because the subtitles aren’t really cracked down on by copyright enforcement (since it’s only text files that you need to have already found the movie to use).
I like your idea of something like an audio track, but only for dialogue/audio that was changed in the translation. This doesn’t really exist, but it’d be cool if it did, especially for stuff like The Simpsons where jokes change to make more sense to different audiences.