I can confirm the same issue too, tried some methods, but I could not get it to launch on proton Experimental on my oled deck.
That's not going to work. SteamWrapped.MethodUtil.ReplaceMethod is relying on implementation details of .NET Framework's JIT.
Looked a bit further. Turns out the method it's trying to replace isn't used anyway. The null reference can be worked around by adding a private method to FNA's GraphicsAdaptor class named IsProfileSupported that takes Enum and GraphicsProfile arguments. It probably trashes memory trying to replace that method, but surprisingly it didn't crash. Then it fails due to inability to read WMA video (Proton loads a test pattern instead, but the game detects it's the wrong size and crashes). That can be worked around by transcoding videos (https://gist.github.com/flibitijibibo/c97bc14aab04b1277d8ef5e97fc9aeff). I encountered one other crash quitting, but I didn't look into that.
Since the native version works, and the Windows version is relying on implementation details of both .NET Framework and XNA (likely not used by any other game) and with a work-around it might randomly start crashing in the future, I don't think it's worth trying to fix.
proton experimentalx2 2024-07
Compatibility Report
System Information
GPU: RX 6700 XT
Video driver version: Mesa 24.1.3
Kernel version: 6.9.10 / 6.6.40
Link to full system information report:
sysinfo_2024_07_23.tar.gz
Proton version: Experimental (2024/07/22), 9.0-2, 8.0-5
I confirm:
Proton log:
Symptoms
Reproduction