Your system information

• Steam client version (build number or date): 1785799196
• Distribution (e.g. Ubuntu): Kubuntu (Ubuntu + KDE) 24.04 LTS
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs:

steam-logs.tar.gz

• GPU: Nvidia + Intel

Hello,

I am having a serious problem with Steam Play / Proton on Kubuntu 24.04. The problem affects multiple Proton games, not just one particular title.

I have already done quite a lot of troubleshooting and I would like to ask whether this could be a Steam/Proton regression, Steam Runtime problem, or an issue related to the current NVIDIA 580 driver and hybrid Intel/NVIDIA graphics setup.

System

• OS: Kubuntu 24.04
• Desktop: KDE Plasma 5.27.12
• Session: X11
• X.Org: 21.1.11
• Kernel: 7.0.0-30-generic
• CPU: Intel Core i7-8850H
• RAM: 32 GB
• iGPU: Intel UHD Graphics 630 (CoffeeLake-H GT2)
• dGPU: NVIDIA Quadro P600 Mobile (Pascal / GP107GLM)
• NVIDIA driver: 580.173.02
• Mesa: 25.2.8-0ubuntu0.24.04.2
• PRIME mode: on-demand
• Proton tested: Proton Experimental, build experimental-11.0-20260826-x86_64

How the problem started

Originally, I was using an older NVIDIA driver (535.x, I believe). Steam and my Proton games worked normally.

After the NVIDIA driver was upgraded to the 580 branch, problems started.

At first I suspected an NVIDIA driver/kernel issue because switching the laptop to: sudo prime-select nvidia

and then launching Steam caused the X11 session to crash and return me to the login screen.

Switching back to: sudo prime-select on-demand

made the desktop stable again.

However, the games still do not work correctly in on-demand mode.

Important: this is not limited to one game

I have tested multiple Proton games and the problem is not specific to Simt Simulator.

One particularly useful example is Euro Truck Simulator 2, which I also run through Proton.

With ETS2, the following happens:

• The first time I launch the game after boot, it can sometimes start and work normally.
• After some time, however, the game can freeze the system so badly that the graphical session becomes completely unresponsive.
• The machine then has to be restarted using REISUB.
• After rebooting, trying to launch ETS2 again fails — the game no longer starts.

This behavior is reproducible enough that I am now concerned that this may be a problem in the Proton / graphics stack rather than an issue with an individual game.

Other Proton games simply fail to start without reaching the game at all.

NVIDIA / Vulkan checks

nvidia-smi reports:
NVIDIA-SMI 580.173.02
Driver Version: 580.173.02
CUDA Version: 13.0

GPU: Quadro P600
Memory: 4096 MiB

The GPU is detected correctly.

vulkaninfo --summary also detects both GPUs:
GPU0:
Intel(R) UHD Graphics 630 (CFL GT2)
driverName = Intel open-source Mesa driver
driverInfo = Mesa 25.2.8-0ubuntu0.24.04.2

GPU1:
Quadro P600
driverName = NVIDIA
driverInfo = 580.173.02

GPU2:
llvmpipe

So the NVIDIA Vulkan driver is installed and the Quadro P600 is visible to Vulkan.

The current PRIME configuration is:
prime-select query
on-demand

The session is:
XDG_SESSION_TYPE=x11
DISPLAY=:0
WAYLAND_DISPLAY=

X11 access control is normal: access control enabled, only authorized clients can connect
SI:localuser:ondra

and the X11 socket exists:
/tmp/.X11-unix/X0

Steam itself works

Steam itself launches normally.

Interestingly, nvidia-smi shows that Steam and Steam WebHelper are actually using the NVIDIA GPU:
/usr/lib/xorg/Xorg
steam
steamwebhelper
steamwebhelper

So NVIDIA PRIME offloading is definitely functioning at least for Steam.

Steam also correctly detects both GPUs:
Intel(R) UHD Graphics 630
driver: Mesa

Quadro P600
driver: NVIDIA proprietary
driver version: 580.173.02

llvmpipe

Therefore this does not look like a simple case where Steam cannot see the NVIDIA GPU.

Proton test

I tested Proton Experimental: experimental-11.0-20260826-x86_64

At one point Proton Experimental managed to start one of the games, but the game had a completely incorrect/unusable resolution. Subsequent attempts failed again.

I also explicitly tested NVIDIA PRIME offloading with: __NV_PRIME_RENDER_OFFLOAD=1 __VK_LAYER_NV_optimus=NVIDIA_only %command%

The game still did not start.

During that test, nvidia-smi showed Steam and Steam WebHelper using the Quadro P600, confirming that the NVIDIA GPU was actually active.

Proton log

I enabled:
PROTON_LOG=1 %command%

This created:

steam-12822364823446618112.log

The Proton log reports:
Proton:
1787725910 experimental-11.0-20260826-x86_64

The most significant error is: err:winediag:nodrv_CreateWindow
Application tried to create a window, but no driver could be loaded.

err:winediag:nodrv_CreateWindow
The explorer process failed to start.

This happens after Wine has already loaded: Loaded "C:\windows\system32\winex11.drv"

There is also:
err:steamclient:steamclient_init_registry
Failed to connect to Steam

and:
Proton: Error: unable to use parent for game drive, path

There is also this message:
Proton: Error while copying to
".../compatdata/2985439455/pfx/drive_c/windows/system32/amdxcffx64.dll":
No such file or directory

The log then continues with many Wine processes being started, but the game never creates a usable window.

Things I have already tested

1. prime-select on-demand

• Desktop remains stable.
• Proton games still fail.

1. prime-select nvidia

• Launching Steam can crash the X11 session and return me to the login screen.

1. NVIDIA 580.173.02

• Currently installed.

1. Vulkan

• vulkaninfo --summary correctly detects the Quadro P600 using NVIDIA 580.173.02.

1. Steam itself

• Launches normally.

1. NVIDIA PRIME offloading

• Steam and Steam WebHelper appear in nvidia-smi, confirming that the NVIDIA GPU is actually being used.

1. Proton Experimental

• Does not reliably launch the games.

1. PROTON_LOG=1

• Reproduces the problem and produces a Proton log.

1. Multiple Proton games

• The problem is not specific to one game.
• Euro Truck Simulator 2 is also affected.

My main question

Could this be a regression or compatibility problem in the current Proton / Steam Runtime / Wine stack when running:

• Kubuntu 24.04
• KDE Plasma 5.27
• X11
• Intel + NVIDIA hybrid graphics
• PRIME on-demand
• NVIDIA 580.173.02
• Quadro P600 / Pascal
• Proton Experimental 11

The particularly suspicious part is:
err:winediag:nodrv_CreateWindow
Application tried to create a window, but no driver could be loaded.

err:winediag:nodrv_CreateWindow
The explorer process failed to start.

even though:

• X11 itself is running normally,
• winex11.drv is loaded,
• Steam itself works,
• Vulkan sees the NVIDIA GPU,
• nvidia-smi works,
• PRIME offloading works.

Additionally, Euro Truck Simulator 2 can sometimes run after the first launch, but can then completely lock up the system, requiring a REISUB reboot, after which the game may no longer start.

I would therefore like to know whether this behavior matches any known issue in Proton, Steam Runtime, Wine, DXVK/VKD3D, or the NVIDIA 580 driver.

I am especially interested in determining whether this is a known regression introduced by the recent Proton / Steam / NVIDIA updates.

I can provide the complete Proton log and any additional diagnostic output you need.

Thank you very much for your help.