Public bug reported:
System:
Ubuntu 26.04 LTS, upgraded from Ubuntu 24.04
GNOME Wayland session
Hybrid Intel iGPU + NVIDIA dGPU laptop
External monitor connected over HDMI
NVIDIA driver 595
Hardware:
Dell Inspiron 7501
NVIDIA GeForce GTX 1650 Mobile / Max-Q
External monitor: Lenovo ThinkVision P24q-10 over HDMI
Problem:
The external HDMI monitor flickers (icons or various sections of the screen)
when using GNOME Wayland on this hybrid Intel/NVIDIA system.
Workaround:
The flickering stops after running:
systemctl --user set-environment
MUTTER_DEBUG_MULTI_GPU_FORCE_COPY_MODE=primary-gpu-cpu
and then logging out and logging back in.
Expected result:
The external HDMI monitor should not flicker in a normal GNOME Wayland session.
Actual result:
The external HDMI monitor flickers unless the Mutter debug copy-mode override
is set.
Additional notes:
This appears related to Mutter multi-GPU copy mode on hybrid Intel/NVIDIA
graphics.
The workaround that fixes the issue is:
MUTTER_DEBUG_MULTI_GPU_FORCE_COPY_MODE=primary-gpu-cpu
My current Mutter experimental features avoid scale-monitor-framebuffer
/ fractional scaling. Fractional scaling may be related, but the key
workaround is the Mutter multi-GPU copy-mode environment variable.
Reproduction steps:
1. Boot into Ubuntu 26.04 GNOME Wayland on the hybrid Intel/NVIDIA laptop.
2. Connect external HDMI monitor.
3. Use the external monitor normally.
4. Observe flickering. It might start at any time, for no particular reason. It
can even start after a day of using it without flickering.
5. Run:
systemctl --user set-environment
MUTTER_DEBUG_MULTI_GPU_FORCE_COPY_MODE=primary-gpu-cpu
6. Log out and log back in.
7. The flickering stops.
Regression / upgrade context:
This system was upgraded from Ubuntu 24.04 to Ubuntu 26.04.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: libmutter-18-0 50.1-0ubuntu2
ProcVersionSignature: Ubuntu 7.0.0-15.15-generic 7.0.0
Uname: Linux 7.0.0-15-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Wed May 20 15:59:23 2026
InstallationDate: Installed on 2025-05-17 (368 days ago)
InstallationMedia: Ubuntu 24.04.2 LTS "Noble Numbat" - Release amd64 (20250215)
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
SourcePackage: mutter
UpgradeStatus: Upgraded to resolute on 2026-04-28 (23 days ago)
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
--
You received this bug notification because you are a member of Ubuntu
Desktop Bugs, which is subscribed to mutter in Ubuntu.
https://bugs.launchpad.net/bugs/2153478
Title:
External HDMI monitor flickers on GNOME Wayland hybrid Intel/NVIDIA;
fixed by MUTTER_DEBUG_MULTI_GPU_FORCE_COPY_MODE
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2153478/+subscriptions
--
desktop-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
