PeerTube doesn't have all of youtube's videos on it

Isn't that PeerTube that's going to be DMCA'd out of existence by Google?

Why? How is it different from yt-dlp from a DMCA standpoint? You're downloading a video in both cases, with this you're not using YouTube’s server bandwidth so it doesn't cost them money.

Because users would also be uploading, as PeerTube works somewhat like Bittorrent.

I never mentioned PeerTube

Whether or not it's actual PeerTube, you're describing something that would have to work like PeerTube, since you can't do peer to peer video sharing without some people uploading, and so inevitably it's going to be DMCA'd out of existence as soon as Google find it.

(Note to self: Never wrestle with a pig ...)

You're not downloading anything you couldn't already download from YouTube with yt-dlp