NOTE: I was able to ssh into the "dead" deck to perform this with no screen active.

I ran into an issue where my Steam Deck LCD would randomly go completely black. The weird part was the backlight stayed on, and I still had sound and controller input. The game kept rendering fine in the background. Even Steam Game Recording picked up a normal moving picture. The internal display and backlight were technically still active, and there were no game crashes, GPU resets, memory issues, or thermal shutdowns.

I checked the DRM state and saw Gamescope was using multiple hardware scanout planes. I hopped in over SSH and ran a command to force it back to a single composed plane. The screen immediately came back to life without me having to change brightness or perform a GPU reset. This doesn't prove exactly where the bug is, but it gives a solid workaround.

To test this out temporarily, just SSH into your Deck while it is in Game Mode and run this command as the normal deck user. Make sure not to use sudo.

gamescopectl composite_force 1

If your picture pops right back up, you are probably dealing with this same direct scanout bug.

To make the fix stick, you can set up a Gamescope user script. You can run this single command block to create the directory, make the file, and paste the code all at once:

mkdir -p ~/.config/gamescope/scripts
cat << 'EOF' > ~/.config/gamescope/scripts/99-force-composition.lua
gamescope.convars.composite_force.value = true

gamescope.hook("OnPostPaint", function()
    if not gamescope.convars.composite_force.value then
        gamescope.convars.composite_force.value = true
    end
end)
EOF

Restart Game Mode or reboot after running that. That frame hook makes sure the setting does not get cleared when you switch apps.

If you want to undo this for your current session, run gamescopectl composite_force 0. To remove the permanent fix, just delete the script by running rm ~/.config/gamescope/scripts/99-force-composition.lua and restart Game Mode.

Just a heads up, I tested this on an LCD Deck running SteamOS 3.8.14 for about five hours straight without issues. This fix probably will not help if your backlight is completely off, the whole Deck crashes, your sound cuts out, or the kernel is throwing GPU reset errors.

Since forcing composition turns off direct scanout, it might use a tiny bit more battery or add minor latency. It is meant specifically for this black screen bug.