We’ve taken down that YouTube project because there were too many edge case bugs with it. It’s purely a project based example so you can still use it but be warned there are mobile and desktop related issues with it.
That project relies on using HTML elements like iframes to work but that is not supported on VR rendering because it doesn’t render HTML elements, only the WebGL context.
However, this user managed to rendering an HTML element to video and rendered that in WebGL: [SOLVED] Multi-threaded operations in WebXR; Editor vs Published (I think)