I'd recommend learning to use yt-dlp to download anything off youtube. As long as you read up on the commands you can download the video in pretty much any format and quality, including strictly audio only versions. If you just search for yt-dlp it should be on a github page with instructions on how to use it.
Edit: Wow, did not notice how old your post was. Hope you see it anyway, its by far the best program I've ever used to archive youtube content.
