Use the
youtube-dl command to download the videos.
Usage examples
Download an entire channel
youtube-dl -citw ytuser:<USER>
Download all videos on a playlist
youtube-dl -citw <PLAYLIST URL>
Download playlist audio only (m4a)
yt-dlp -f 140 -o "%(playlist)s/%(playlist_index)s - %(title)s.%(ext)s" "<PLAYLIST URL>"
Links
http://rg3.github.io/youtube-dl/index.html
https://github.com/rg3/youtube-dl/
https://github.com/ytdl-org/youtube-dl