yt-dlp error "No video formats found" and how I learned about DASH and that my yt-dlp filter could be improved

I participated in an only workshop at the weekend and the organisers kindly provided the recording as an unlisted YouTube video. As I wanted to watch the video again at a later time I used my MeTube installation to download the YouTube video. Or rather: Tried to. As the download would fail. MeTube would say no available formats could be found. The video however played nicely on YouTube!? The setup I use a self-hosted web frontend for yt-dlp in Docker called MeTube, configured through the YTDL_OPTIONS environment variable. My config looked like this: YTDL_OPTIONS={ "cookiefile":"/downloads/cookies/cookies.txt", "format-sort": "res:1080", "format": "best[language^=de]/best[language^=en]/b", "merge_output_format": "mp4" } The idea behind this filter was: Limit video to 1080p in quality (not higher) Use the best available version with German audio Else use the best available version with English audio Use whatever is available as fallback Step 1: Debugging Naturally my first move was to…