Created attachment 156460 [details]
Journal output

SUMMARY
I have a dual monitor setup (4k primary + FHD). Both monitors are connected to a power strip with a switch. 
When I turn them off and on again, KDE disables the primary 4k monitor and only the FHD monitor is active. The other monitor goes black and only the mouse is visible. (This does not happen when I switch off the monitors using the power button.)

When I press CTL+ALT to switch to the console, both monitors are reactivated, but only in console mode.
When I restart sddm in this mode, sddm is displayed correctly on both monitors.
When I log in, the primary 4k monitor is disabled and the desktop launches on the FHD monitor.

When I try to enable the 4k monitor via the KDE display manager, nothing happens, or the monitor is enabled and KDE crashes, then reverts back to the FHD monitor.
When I reboot, nothing changes.
If I start the nvidia x server settings and enable the 4k monitor, it works again.

This bug appeared last year. Affected versions are definitely 5.27, 5.26 and 5.25. There are probably more affected versions, but I cannot remember which version broke it. It worked fine in the past. The issue appeared with Neon 20.04 and stayed with 22.04.
The only clue I have is that the German translation of the display manager utility was missing after the update when the bug first appeared. 

I have attached the journal log between the point where I turn off the monitors, turn them back on and log in via console to save the log.

STEPS TO REPRODUCE
1. Hard power off the monitors
2. Turn them on again

OBSERVED RESULT
Primary 4k monitor gets disabled
Secondary FHD monitor becomes primary

EXPECTED RESULT
Monitor setup restored

SOFTWARE/OS VERSIONS
Operating System: KDE neon 5.27
KDE Plasma Version: 5.27.0
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Kernel Version: 5.19.0-32-generic (64-bit)
Graphics Platform: X11
Processors: 16 × AMD Ryzen 7 1700 Eight-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1080 Ti/PCIe/SSE2
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: AX370-Gaming 5
Nvidia driver: 510.47.03-0ubuntu1

ADDITIONAL INFORMATION
xrandr output when it is working:
Screen 0: minimum 8 x 8, current 5760 x 2160, maximum 32767 x 32767
DVI-D-0 connected 1920x1080+3840+0 (normal left inverted right x axis y axis) 510mm x 290mm
   1920x1080     60.00*+
   1680x1050     59.95  
   1600x900      60.00  
   1440x900      59.89  
   1400x1050     59.98  
   1280x1024     75.02    60.02  
   1280x800      59.81  
   1280x720      60.00  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32    56.25  
   640x480       75.00    59.94  
HDMI-0 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
   3840x2160     60.00*+  30.00  
   1920x1080     60.00    59.94  
   1600x900      60.00  
   1280x1024     60.02  
   1280x800      59.81  
   1280x720      60.00    59.94  
   1152x864      59.96  
   1024x768      60.00  
   800x600       60.32  
   720x480       59.94  
   640x480       59.94    59.93  
DP-3 disconnected (normal left inverted right x axis y axis)