There is still no functional VR media player for linux, none of the Windows ones work with Proton and the official SteamVR Media Player has no linux release.
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.
Just to make sure we're talking about the same fix, do you mean running the LAV installer first (edit: followed by selecting DirectShow in the options)? That worked for me with Proton 5.13-6.
Welp I got curious whether I'd missed a step so I gave it a once over, took me 7 hours to get it working. Turns out Proton does not like to run from an NTFS partition so I reinstalled steam on ext4. Now it runs but I couldn't get Direct Show to work, only the VLC video-path. I assume the LAV installer failed somehow. I also had to mount bind my external drive in my home folder otherwise it wouldn't see it. And I also had to reset whirligig's settings manually in the prefix folder (steamapps/compatdata/451650/pfx/drive_c/users/steamuser/Application Data/Whirligig/production) because it randomly stops accepting inputs.
Just writing it all out in case somehow comes across it.
