Hammer Bug: hammer map launcher doesnt mount portal 2 when ran through proton

[Fran12334]

Describe the bug

If hammer is opened through the sdk launcher in steam using proton, when building the map vvis and vrad do not find portal 2 as a game to mount which leads to missing props and portal 2's textures being fully lit. This does not happen if the sdk launcher or hammer itself are opened through wine.

Textures that are not from portal 2 seem to work fine. This issue is particularly important for anyone on a steam deck where running hammer through wine is much harder or impossible.

To Reproduce

1. Open hammer through sdk launcher using proton.
2. Build a map that uses portal 2's textures.
3. Run the map.
4. See that the textures are fully lit.

Issue Map

These are the console outputs that happen when running hammer map launcher through wine and proton respectively. Any map that uses portal 2's textures will do, i tried uploading a map here but github wouldn't allow me.

You can see that in the case of the wine log FileSystem_Init::MountGames: Successfully mounted game AppID 620 with 8 subfolders and/or VPKs. appears. This does not happen in the proton log, but there also arent any errors in its place.
wine.txt
proton.txt

Expected Behavior

When ran through proton, hammer map launcher should have the same behavior as when launched through wine.

Operating System

CachyOS