Lately Youtube too annoys me with some message to sign up if I'm not logged in. Unfortunately, that is not a popup, it is displayed in the video panel, stopping the video from playing.
This kind of BS (along with other UX annoyances with the official YouTube) finally convinced me to run my own instance. No more problems since then.
YouTube has been annoying me much lately (especially when all videos start playing at low quality for the few first seconds) but this really is the last straw. Unfortunately all videos on the internet are there. So all I can do about it is bark here. Woof woof.
youtube-dl
and changing the URL to read youtube.com/embed/NUMBER
Maybe it isn't available in their region, maybe they do not have or want an account or agree with the company's privacy policy, and finally if they clear cookies regularly then an account still won't solve their problem as they'd have to login each time to dismiss the popup.
Donate the $ to archive.org .
It will work for a long time. If it breaks, just follow this 30 sec guide. https://www.youtube.com/watch?v=8TvCGWwQr5o