Very interesting. I tested primarily on Firefox Windows and iOS and I don’t see similar complaints by others so I suspect it is working widely… I wonder if you have an extension which could be disabling the JavaScript?

It is especially weird that “background-attachment: fixed” wouldn’t work on desktop though since that is old old technology.

Are you sure you are seeing the light ray texture at all? If you aren’t sure, you could try boosting your screen brightness. It’s a very subtle effect.

Otherwise, it would be useful to know if your console shows any error messages on the page.