Read a YouTube channel instead of watching it. Runs entirely on your own computer.
Nobody was asked which language the channel speaks — it is read from the videos.
One sentence, said once, an hour and a half into a four-hour stream from two years ago. Nobody was ever going to find that by watching.
Optional. Tell it what you already know, and a model on your own machine reads the whole corpus against it. Most videos produce nothing — that is the point.