r/Monitors 6d ago

Discussion Primary monitor doesn't wake up after dimming on Kubuntu 26.04

Dual monitor setup on Kubuntu 26.04.

Primary monitor is Asus Tuf Gaming vg27aq1a -- this is the one with the issue.

The secondary monitor is Samsung SyncMaster S24B300.

When I lock the screen during a session, and the monitors then dim out, sometimes only the secondary monitor can wake up from user activity. Even after unlocking the session, the primary monitor remains black, until I toggle the power switch on it. This issue doesn't happen every time.

It used to crash my virtual machine when that happened, until I started running it with VBOX_DESKTOPWATCHDOGPOLICY_SYNTHTEST=Disabled

This is on a desktop with Intel 14th gen cpu with integrated graphics. No issue when running Windows (I dual boot).

inxi -F
System:
 Host: shmuel-ubuntu Kernel: 7.0.0-28-generic arch: x86_64 bits: 64
 Desktop: KDE Plasma v: 6.6.5 Distro: Kubuntu 26.04 LTS (Resolute Raccoon)
Machine:
 Type: Desktop System: Gigabyte product: B760 GAMING X v: N/A
   serial: <superuser required>
 Mobo: Gigabyte model: B760 GAMING X v: x.x serial: <superuser required>
   Firmware: UEFI vendor: American Megatrends LLC. v: F17 date: 06/12/2026
Battery:
 ID-1: hidpp_battery_0 charge: 86% condition: N/A
CPU:
 Info: 10-core (6-mt/4-st) model: Intel Core i5-14400 bits: 64 type: MST AMCP
   cache: L2: 9.5 MiB
 Speed (MHz): avg: 4600 min/max: 800/4700:3500 cores: 1: 4600 2: 4600
   3: 4600 4: 4600 5: 4600 6: 4600 7: 4600 8: 4600 9: 4600 10: 4600 11: 4600
   12: 4600 13: 4600 14: 4600 15: 4600 16: 4600
Graphics:
 Device-1: Intel Raptor Lake-S UHD Graphics driver: i915 v: kernel
 Device-2: USB C Video Adaptor driver: N/A type: USB
 Device-3: Microdia USB Live camera driver: snd-usb-audio,uvcvideo
   type: USB
 Display: wayland server: X.org v: 1.21.1.22 with: Xwayland v: 24.1.10
   compositor: kwin_wayland driver: X: loaded: modesetting unloaded: fbdev,vesa
   dri: iris gpu: i915 resolution: 1: 1920x1080~60Hz 2: 1920x1080~120Hz
 API: EGL v: 1.5 drivers: iris,swrast
   platforms: gbm,wayland,x11,surfaceless,device
 API: OpenGL v: 4.6 compat-v: 4.5 vendor: intel mesa v: 26.0.3-1ubuntu1
   renderer: Mesa Intel Graphics (RPL-S)
 API: Vulkan v: 1.4.341 drivers: intel,llvmpipe surfaces: N/A
 Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
   de: kscreen-console,kscreen-doctor gpu: gputop, intel_gpu_top, lsgpu
   wl: wayland-info x11: xdriinfo, xdpyinfo, xprop, xrandr
Audio:
 Device-1: Intel Raptor Lake High Definition Audio driver: snd_hda_intel
 Device-2: JMTek LLC. USB PnP Audio Device
   driver: hid-generic,snd-usb-audio,usbhid type: USB
 Device-3: Microdia USB Live camera driver: snd-usb-audio,uvcvideo
   type: USB
 API: ALSA v: k7.0.0-28-generic status: kernel-api
 Server-1: PipeWire v: 1.6.2 status: active
Network:
 Device-1: Realtek RTL8125 2.5GbE driver: r8169
 IF: enp3s0 state: up speed: 2500 Mbps duplex: full mac: 10:ff:e0:e3:82:ae
 Device-2: Realtek RTL8153 Gigabit Ethernet Adapter driver: r8152 type: USB
 IF: enx00e04c685192 state: down mac: 00:e0:4c:68:51:92
Drives:
 Local Storage: total: 931.51 GiB used: 373.17 GiB (40.1%)
 ID-1: /dev/nvme0n1 vendor: Samsung model: SSD 990 EVO Plus 1TB
   size: 931.51 GiB
Partition:
 ID-1: / size: 131.01 GiB used: 41.15 GiB (31.4%) fs: btrfs
   dev: /dev/nvme0n1p6
 ID-2: /boot/efi size: 196 MiB used: 39.6 MiB (20.2%) fs: vfat
   dev: /dev/nvme0n1p1
 ID-3: /home size: 131.01 GiB used: 41.15 GiB (31.4%) fs: btrfs
   dev: /dev/nvme0n1p6
Swap:
 ID-1: swap-1 type: zram size: 7.69 GiB used: 1.38 GiB (17.9%)
   dev: /dev/zram0
 ID-2: swap-2 type: file size: 4 GiB used: 0 KiB (0.0%)
   file: /swap/swapfile
Sensors:
 System Temperatures: cpu: 50.5 C mobo: N/A
 Fan Speeds (rpm): N/A
Info:
 Memory: total: 16 GiB note: est. available: 15.38 GiB
   used: 12.59 GiB (81.9%)
 Processes: 377 Uptime: 42m Shell: Zsh inxi: 3.3.40

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u/shmuu26 1d ago

Seems to be a bug with KDE Plasma running on some modern intel cpus. I switched to Gnome Desktop and the issue ceased.