youtube-dl, a tool to download YouTube videos. Using
apt installs a
version that's too old to work, so:
pipsi install youtube-dl
Download the video from YouTube:
This results in a webm file. I have no idea what that is, and am relieved to discover that converting it into an mp3 requires just:
ffmpeg -I MyVideoFile.webm -vn MyAudioFile.mp3
-vn disables video in the output.