looking for help on multimonitor setup

[Django Reinhard]

Hi,

I was an enthusiastic user of xinerama mode, but for some time now kde crashes
when xinerama is activated.
That's why I'm looking for working alternatives.

Supposedly xrandr can take over this functionality, but I can't get it to work.
I am attaching the output of xrandr so that you can see what my setup looks like.

I found a setup in the Ubuntu wiki that seems reasonable, but when I use it, only
the center monitor displays part of the desktop.
Right and left remain black.

What am I missing?

Setup:
--------
Grafic card: 	NVIDIA TU116 [GeForce GTX 1660 SUPER]
driver: 	nvidia
System:	Kernel: 6.12.8-1-liquorix-amd64 [6.12-10~mx23ahs]
arch: 	x86_64 bits: 64 compiler: gcc v: 12.2.0
Desktop: 	KDE Plasma v: 5.27.5 wm: kwin_x11 vt: 7 dm: LightDM v: 1.32.0
nvidia-driver:	535.216.03-2~mx23ahs

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$>xrandr
Screen 0: minimum 8 x 8, current 3600 x 1920, maximum 32767 x 32767
DP-0 connected primary 1200x1920+1200+0 left (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    50.00
   1680x1050     59.95
   1600x900      60.00
   1440x900      59.89
   1280x1024     60.02
   1280x800      59.81
   1280x720      60.00    50.00
   1024x768      60.00
   800x600       60.32    56.25
   720x576       50.00
   720x480       59.94
   640x480       59.94
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected 1200x1920+0+0 left (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    50.00
   1680x1050     59.95
   1600x900      60.00
   1440x900      59.89
   1280x1024     60.02
   1280x800      59.81
   1280x720      60.00    50.00
   1024x768      60.00
   800x600       60.32    56.25
   720x576       50.00
   720x480       59.94
   640x480       59.94
DP-3 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)
DP-5 connected 1200x1920+2400+0 left (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    50.00
   1680x1050     59.95
   1600x900      60.00
   1440x900      59.89
   1280x1024     60.02
   1280x800      59.81
   1280x720      60.00    50.00
   1024x768      60.00
   800x600       60.32    56.25
   720x576       50.00
   720x480       59.94
   640x480       59.94
HDMI-A-1-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1-0 disconnected (normal left inverted right x axis y axis)
DisplayPort-1-1 disconnected (normal left inverted right x axis y axis)
DisplayPort-1-2 disconnected (normal left inverted right x axis y axis)

$> xrandr --listmonitors
Monitors: 3
 0: +*DP-0 1200/518x1920/324+1200+0  DP-0
 1: +DP-2 1200/518x1920/324+0+0  DP-2
 2: +DP-5 1200/518x1920/324+2400+0  DP-5
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Section "InputDevice"
        Identifier      "Generic Keyboard"
        Driver          "kbd"
        Option          "XkbRules"      "xorg"
        Option          "XkbModel"      "pc105"
        Option          "XkbLayout"     "us"
        Option          "XkbOptions"    "lv3:ralt_switch"
EndSection

Section "InputDevice"
        Identifier      "Configured Mouse"
        Driver          "mouse"
        Option          "CorePointer"
        Option          "Emulate3Buttons"       "no"
EndSection

Section "Device"
     Identifier     "Configured Video Device"
     Driver         "nvidia"
     VendorName     "NVIDIA Corporation"
     BoardName      "NVIDIA GeForce GTX 1660 SUPER"
     BusID          "PCI:1:0:0"
     Option         "ConnectedMonitor" "DFP"
     Option         "Monitor0" "Left Monitor"
     Option         "Monitor1" "Center Monitor"
     Option         "Monitor2" "Right Monitor"
#     Option "RegistryDwords" "EnableBrightnessControl=1"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Left Monitor"
    VendorName     "Samsung"
    ModelName      "Samsung S24E650"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 60.0
    Option         "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Center Monitor"
    VendorName     "Samsung"
    ModelName      "Samsung S24E650"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 60.0
    Option         "DPMS" "true"
    Option         "RightOf" "Left Monitor"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Right Monitor"
    VendorName     "Samsung"
    ModelName      "Samsung S24E650"
    HorizSync       30.0 - 81.0
    VertRefresh     56.0 - 60.0
    Option         "DPMS" "true"
    Option         "RightOf" "Center Monitor"
EndSection

Section "Screen"
   Identifier      "Default Screen"
   Device          "Configured Video Device"
   DefaultDepth    24
   SubSection "Display"
      Depth        24
      Virtual      3600 1920
   EndSubSection
EndSection

Section "ServerLayout"
        Identifier      "Default Layout"
        Screen          "Default Screen"
        InputDevice     "Generic Keyboard"
        InputDevice     "Configured Mouse"
EndSection