I think its for subscribing to channels, but It would download the videos locally. if you need to backup a whole channel then maybe yt-dlp would be a better tool?

You can subscribe to channels, or download individual videos. There is browser extension that puts a download button on youtube.com

It's a complete web application with search and web-player where you have your own local video platform with those videos vs. yt-dlp which is just a command line download tool.

When downloading a lot, be aware of countermeasures by YT. IPs get blocked and user login will be required. I had YT video playback deactivated on my YT account for a few days.