with Proton and from a browser, I also get the "login for my protection" message.
However, on NewPipe it is working flawlessly.
DeletedUser69 have you tried to "disable piped proxy" (settings/insances/proxy/'disable piped proxy toggle'
This would then fetch the content directly from Youtube servers, so maybe best to use with a VPN as indicated in the app. With this setup (ProtonVPN + LibreTube with piped proxy disabled), I am able to watch videos.