youtube-dl (and yt-dlp) has a flag, I believe -G, which gives you the URL(s) for the requested format/quality. I used the command line on my computer and put the link in VLC. On my phone I had this elaborate workaround involving downloading the file to my VPS first over SSH, then downloading it to my phone, until I realized my phone browser can consume the URL directly, so I set up a PHP frontend for `youtube-dl -G -f bestaudio {url}`
It's no longer online and I lost the code, but it was like one line of code.
I mention this because you-get seems to support the same usecase (via --url / -u), so I wanted to let people know how useful this is!
(While it was online I shared it on some forums and got very positive feedback, people used it for audiobooks etc.)
[0] Also playing with screen off saves 80% battery life! YouTube knows these facts and that's why they made background playback (which fetches only audio stream) a paid feature...