Afrer reading the description, this project seems to be solely focused on downloading all of a specific channel's videos. I've been taking my first steps at having a home server, and one of the things I'd love to do with it is having an archive of the videos that I have saved in my private playlists on YouTube. In my mind, the service would periodically check all my playlists, compare with what exists locally, and do…
Yark will be able to do this in v1.3 releasing in ~1 month provided it has access to the playlists, I'm not sure how to do creds currently but I'll look into it. Issue for downloading playlists: https://github.com/Owez/yark/issues/49
For auth it seems the preferred way to login with Google is OAuth2, that's I believe what third-party apps use, e.g. Thunderbird uses it when setting up a new GMail account.
However, for apps that don't support OAuth2, there is also the possibility of using "App Passwords" [1], I've used one in the past and it worked well. (Update: I'm just reading it only works if 2FA is enabled, which I use)
[1]: https://support.google.com/accounts/answer/185833?hl=en