I ran into that as well on AMD hardware. It seems to have resolved itself for me.
I think someone else I know ran into a similar issue on Windows. It seems to be a bug with the game that's much more prevelant on Linux.
Just wanted to note here that I'm having this issue on NVIDIA hardware now 5080 (my friend reported not having any issues on AMD hardware) and there's an odd detail in that only some of the menus are affected.
vs
This is what the upgrade screen (the white one) is supposed to look like: https://youtu.be/fVnVHHT6RB0?t=97
So it seems to be a missing codecs thing that maybe works for AMD (once the shader cache has the converted video present or using Proton GE which doesn't need the converted video cache?) but not for NVIDIA.
proton experimentalx1 2026-04
Compatibility Report
System Information
I confirm:
steam-1430190.log
Symptoms
Background videos during shader loading and in the main menu do not load and display a white background.
You can see several mfplat errors in the log at each step, as well as raw AAC codec errors.
Reproduction
This can be reproduced every time the game is launched. Just get to the shader loading screen, and you'll already see the white screen.