yt-dlp -f "bv*[vcodec^=avc1][ext=mp4]+ba[acodec^=mp4a][ext=m4a]/best[ext=mp4][vcodec^=avc1]" \ --merge-output-format mp4 \ -o "%(title)s.mp4" \ "YOUTUBE_URL_HERE"

Thanks. I played around with your idea and got this. It’s still not 100% of videos. Only YouTube videos that have any H.264+AAC stream available (which is 99.9% of public YouTube today, even if the main/default version is VP9 or AV1).

But re encoding to solve this is not required. I stand corrected.