Using youtube-dl on iPad (now yt-dlp)
This is really a great tip by Greg Godwin:
I also get it working in two minutes, just got a warning to update pip to 20.3 version
pip install --upgrade pip
Upgrade youtube-dl with this command:
pip install --upgrade youtube-dl
via: Macstories

Update
(2022.02.06) You can install also yt-dpl (a youtube-dl fork with additional features and fixes) with this command:
pip install --no-deps -U yt-dlp
To update re-run the same command.