This build is based upon @mohamadaljaf's patches from proton bug report 8457 and 6533. It enables the games Pirates VR: Jolly Roger and Desperate: Vladivostok to work on Linux.
They implement a number of interfaces/functions from HolographicSpace as stubs, preventing the errors that would otherwise made an unreal engine error dialog appear. With this, both games start normally (tested with SteamVR via Steam Link so far) and are completely playable.
The patches from Mohamad (3 patches in total) are also included, in case you want to build your own version of proton. These should be applied against Proton's "proton_10.0" branch from the repository.
To install: First exit Steam, then uncompress protola-10.0.tar.gz under ~/.local/share/Steam/root/compatibilitytools.d -- it should create a new directory protola-10.0 there. Then restart Steam, go to the game's properties, tab "compatibility tool", and amongst the options you should have "protola 10".
As for Mohamad's patches, apply them in sequence (I used patch -p1) under the wine tree of Proton.
For some gameplay sample of Pirates VR: Jolly Roger running on Linux: https://www.youtube.com/watch?v=TGT71f40dMg
I curate Linux VR Games on Steam, you can subscribe to my curator here: https://store.steampowered.com/curator/45753882-VR-Linux/
