yt-dlp -f "bv*[vcodec^=avc1]+ba[acodec^=mp4a]/b[ext=mp4]" --merge-output-format mp4 URL

yt-dlp -f "bv*[vcodec^=avc1][height<=480]+ba[acodec^=mp4a]/b[height<=480][ext=mp4]" --merge-output-format mp4 URL