Title: Brightness control not working on Wayland with AMD+NVIDIA hybrid GPU (Dell G15 5525)

General Help
1

Hi,

I'm running Zorin OS 18.1 (based on Ubuntu 24.04 Noble) with kernel 6.17.0-29-generic on a Dell G15 5525 with hybrid GPU (AMD Radeon integrated + NVIDIA discrete).

Brightness control works perfectly on X11 with acpi_backlight=native in GRUB. However, on Wayland the slider appears in Settings but has no effect.

Diagnosis:

The backlight devices exposed under /sys/class/backlight/ are amdgpu_bl2 and nvidia_0, both of type raw. Since logind only manages backlight devices of type firmware or platform, it ignores raw devices on Wayland, causing the GNOME slider to have no effect.

The GNOME Settings Daemon is also disconnected from the device — gdbus calls to org.gnome.SettingsDaemon.Power.Screen return a brightness value but do not actually change the screen brightness.

Writing directly to /sys/class/backlight/amdgpu_bl2/brightness works fine via terminal, confirming the device itself is functional.

Relevant dmesg output:

[drm] Using custom brightness curve
*ERROR* dc_dmub_srv_log_diagnostic_data: DMCUB error - collecting diagnostic data

System info:

  • Zorin OS 18.1 (Noble)
  • Kernel: 6.17.0-29-generic
  • GNOME Shell: 46.0
  • GPU: AMD Radeon (integrated) + NVIDIA (discrete)
  • Backlight devices: amdgpu_bl2, nvidia_0 (both type raw)
  • Session type: Wayland (confirmed via busctl)

Note: Kernel 6.8 is not an option as it breaks the touchpad and other hardware on this machine.

Is there a known fix or workaround for this? Thank you.

2

Hi and welcome.

Don't know if this is of any help:

In the meantime, don't forget to download the Unofficial Manual (still a work in progress) from here:

3

Welcome to the Forum!

Are Secure Boot and Fast Boot in BIOS disabled? One Option would be to use X11 instead of Wayland.

But when You want stay on Wayland ... You could try it with installing brightnessctl. You can install it with sudo apt install brightnessctl

Or You could try this Gnome Extension:

4

Why not use X11? Do you have other problems there?

5

No, because Wayland is the future, X11 has problems with Unreal Engine 5 pop-ups.

6

Unfortunately, I tried all these solutions but nothing worked. It's strange that with Ubuntu 24.04 and 26.04 with Wayland, simply setting acpi_backlight=native in GRUB works.

7

But I thought you were having issues in both Wayland and X11 (xorg)?

With regards X11 and Unreal Engine issue, I used a Brave A.i. search and found this:

" There is no specific native configuration in Unreal Engine 5 to disable or resolve popup issues unique to the X11 windowing system; the engine primarily targets Windows and macOS, with Linux support often relying on the proprietary NVIDIA driver or Vulkan backend.

Common "popup" or windowing glitches reported by UE5 users on Linux (X11) are typically caused by NVIDIA Multi-Process Optimization (MPO) or Multi-Frame Sampled AA (MFAA) conflicts with the display server.

To resolve these issues, apply the following workarounds:

  • Disable NVIDIA MPO : This is the most reliable known workaround for UI flickering, frozen popups, and window management errors on Linux. Follow the Nvidia Support Knowledge Base instructions to disable the MPO feature in your GPU driver settings.

  • Disable MFAA for the Editor : If the editor spawns black screens or unwanted windows, go to the NVIDIA Control Panel , navigate to Manage 3D Settings , select Unreal Editor in the Program Settings, and set Multi-Frame Sampled AA (MFAA) to Off .

  • Switch Display Backend : If using the proprietary NVIDIA driver, try switching the engine to use the Vulkan backend instead of the default, as this often bypasses X11-specific compositor bugs.

  • Disable Editor Notifications : If the "popups" refer to in-editor notifications (e.g., "Compiling C++ Code"), disable them by adding Slate.bAllowNotifications=0 to your ConsoleVariables.ini or the editor console.

If the issue persists, ensure your NVIDIA drivers are up to date, as older versions have been linked to these X11 rendering artifacts.

AI-generated answer. Please verify critical facts."

1 Like
8

Did you run 'sudo update-grub' after you added it to grub in Zorin and reboot?

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9

I appreciate your support. I've already tried several alternatives to Unreal Engine 5 with Wayland, and it's been working very well without any UI crashes. I've tried all the options recommended, even by Claude within X11, but all were unsuccessful. In the end, Wayland became the safe haven. However, the focus here is on monitor brightness in Wayland. This seems to be a bug in Zorin OS 18.1, since it's working with other dists like Pop!_OS and Ubuntu. It's a shame because it was the only one that didn't work, as I find Zorin OS 18.1 wonderful and didn't want to have to remove it.

1 Like