Not sure what you mean, but there is the open source vr-video-player [0] that works with YouTube, can put flat games on a virtual big screen, etc. Works great.
I found it in a round about way too, could use some better publicity maybe. You can also use this to enable side-by-side 3D in VR, so like the old Nvidia 3D shutter glasses that made games pop out of a flat screen, you can see that in your virtual screen in VR. Take a look at SteamTinkerLaunch [0] to set that up (currently helping organize that giant readme, but the info is all there to play around with [1]).
Edit: I should say side-by-side mode works for games with it builtin (like Trine) but can also use shader injection to emulate this which can work pretty well too.
[0] https://git.dec05eba.com/vr-video-player/about/