Porteus

YouTube-dl can no longer download age-restricted videos
Please refer:
https://github.com/ytdl-org/youtube-dl/issues/28578

An alternative: FreeTube
FreeTube is an open source desktop YouTube player built with privacy in mind. Use YouTube without advertisements and prevent Google from tracking you with their cookies and JavaScript.

Download (.deb .rpm Appimage):
https://freetubeapp.io/#download

Usage:
https://docs.freetubeapp.io/usage/

Thanks for the highlight on that useful package.

A very good alternative: https://9xbuddy.com
You can download from almost any video hosting site using 9xbuddy.
See #11 by Rava:
Using ffmpeg to record what comes from the web browser (Post by donald #61551)