For most of its existence, the Youtube TV interface, used by many smart home devices as an HTML5 interface to Youtube was publicly accessible to all at
Sadly, for some reason that eludes me, Youtube has discontinued this feature. Or so it would seem. If your browser spoofs its user agent string to one used by a Smart TV device, the app still works.
I’ve tried many browser extensions dedicated to spoofing before deciding I’d write my own, since its purpose is very simple and no user interface is required.
Check it out at https://github.com/ticklemynausea/youtube-tv-ua-spoof.