UE 5.7 Linux Editor makes desktop unclickable when launched through Docker

Development Getting Started & Setup
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Hi, I’m testing Unreal Engine 5.7.4 on Linux through Docker and running into a severe input issue.

System:

  • OS: CachyOS

  • Desktop: KDE Plasma on X11

  • GPU: NVIDIA RTX 3070

  • Docker image: ghcr.io/epicgames/unreal-engine:dev-5.7

  • Engine version from logs: 5.7.4-51494982+UE5

Issue:
The editor launches successfully, but when I click into the Unreal Editor window, my entire desktop becomes unclickable. I cannot click the editor, KDE panel, other windows, or anything else. Keyboard shortcuts like Alt+F4 and Ctrl+Alt+Esc also did not recover it, and I have to hard restart with the power switch. This is 100% reproducible.

I tried switching to opengl but, the crash still occurred.

Docker launch command:

docker run --rm -it \
  --gpus all \
  --ipc=host \
  -e DISPLAY="$DISPLAY" \
  -e SDL_VIDEODRIVER=x11 \
  -v /tmp/.X11-unix:/tmp/.X11-unix \
  -v "$HOME/UnrealDocker/Projects:/home/ue4/Unreal Projects" \
  ghcr.io/epicgames/unreal-engine:dev-5.7 \
  bash -lc '/home/ue4/UnrealEngine/Engine/Binaries/Linux/UnrealEditor "/home/ue4/Unreal Projects/MyProject/MyProject.uproject" -windowed -ResX=1280 -ResY=720 -opengl4; bash'

Workaround discovered:

If I run Unreal inside Xephyr (virtual monitor), the input issue does not occur:

Xephyr :2 -screen 1600x900 -resizeable

Then launching Unreal with:

-e DISPLAY=:2
-e SDL_VIDEODRIVER=x11
-opengl4

allows me to click and interact with the editor safely inside the nested X window.

However, when using Xephyr with Vulkan, Unreal crashes with:

LogVulkanRHI: Error: Result failed, VkResult=-4
VK_ERROR_DEVICE_LOST
FVulkanDynamicRHI.TerminateOnGPUCrash

Question:

Any ideas what is happening? I’m at a loss of what to do.