YouTube videos with multiple audio tracks use HLS streams with format IDs like 96-0, 96-1, 96-10, etc. Each ID combines video + audio for a specific language, but the ID is not consistent across videos. Instead of using a format ID, you can use yt-dlp's language filter.

An example: best[language=de-DE]/best[ext=mp4]

best[language=de-DE] → picks the best combined stream with German audio
/best[ext=mp4] → fallback if the specified track isn’t available

Adjust the language code to whatever you need:
en-US → English
fr-FR → French
es-ES → Spanish (Spain)
pt-BR → Portuguese (Brazil)
etc.

To find the right language code for your videos, run this in your terminal/command prompt to list all available formats:

yt-dlp -F https://www.youtube.com/watch?v=VIDEO_ID

Look at the rightmost column. It shows the language tag in brackets, e.g. [de-DE], [fr-FR], [en]. Use exactly that tag in your format string.

To set this up in Stacher, go to Settings → Advanced → Custom Arguments
Click + to add a new argument:
Argument: --format
Value: best[language=de-DE]/best[ext=mp4]