The developers are not responding to the issue, and from what I understand it is borderline impossible to fix, because there is an entire security team behind the Google login protection. The only workaround is to login with a browser and copy the cookies from it to youtube-dl.
I'm pretty sure that is what they mean, yes. It is a nice tool. Lets you write HTTP(S) templates with parameters and whatnot, save them in groups, send them, handle the response, etc.
Why not simply create a youtube-login command that does nothing but launch an electron instance that lets you login into youtube and then returns the cookie?
youtube-dl could then call that command to obtain the cookie.
Content with a certain age threshold triggers login. The last time I looked at this, embedding these videos was still possible without logging in. So there are definitely ways in accessing the content without authentication.
Hm. If embedding works maybe my ad-blocking is sufficient; or I just haven't come across any that require it. I mostly just watch woodworkers/machinists/electronics/etc. Sort of conceivable it could be age restricted but would also be surprising.