Other than a few commits [1], everything in youtube-dl is already in yt-dlp. You can see upto which upstream commit is merged into yt-dlp in the changelog [2]

[1] https://github.com/yt-dlp/yt-dlp/issues/21 [2] https://github.com/yt-dlp/yt-dlp/blob/master/Changelog.md#20...