>>599のURLに音はちゃんと入ってるし、落ちるじゃないか

youtube-dlは-Fで↓見えるし、-f 映像+音声で落とせば入る
[info] Available formats for master:
format code extension resolution note
audio-0-en__Main_ mp4 audio only [en]
audio-1-en__Main_ mp4 audio only [en]
audio-2-en__Main_ mp4 audio only [en]
audio-3-en__Main_ mp4 audio only [en]
336 mp4 480x270 336k , avc1.420015, video only
631 mp4 960x540 631k , avc1.4d001f, video only
994 mp4 1280x720 994k , avc1.4d001f, video only
1921 mp4 1920x1080 1921k , avc1.640028, video only (best)

streamlinkは-l debugで↓見えるし、落とせば入る
[stream.hls][debug] Using external audio tracks for stream 270p (language=en, name=en (Main))
[stream.hls][debug] Using external audio tracks for stream 540p (language=en, name=en (Main))
[stream.hls][debug] Using external audio tracks for stream 720p (language=en, name=en (Main))
[stream.hls][debug] Using external audio tracks for stream 1080p (language=en, name=en (Main))
Available streams: 270p (worst), 540p, 720p, 1080p (best)

どっちもffmpegと(youtube-dlには)ffprobeも必要