I set this up recently (the 'Play with MPV' method) after noting that viewing YouTube in the browser had a far greater CPU usage than watching the same in mpv.

I've also given gtk-youtube-viewer a spin but it doesn't do "new videos of your subscriptions" (though it's command=line equivalent 'youtube-viewer -SV' does). Any recommendations out there for similar YouTube frontends?

Also, at least in the UK, youtube-dl can access BBC iPlayer content without the login required on the web.