if you feel the need, make a backup of the file:

/var/lib/sddm/.config/kwinoutputconfig.json

Delete the file.

After a reboot you should have a new file containing only the current monitor configuration.

The following sections (found in the bottom half of the file) are defined in the same order as the monitor definitions found in the first half of the file.

Here I have 2 monitors and I want the one on the left to be ‘off’ with the primary monitor to the right ‘on’ and login input focus.

My primary monitor is the first definition in the snippet below under ‘outputs’: , and is the monitor I want on the right, so below I change the x: position x: 1920. Adjust to the native pixel width of your left hand side monitor.

The left monitor, with output index 1 below, needs to have position x: 0. (if you didn’t get it by now, X starts at the left so whichever monitor you want on the left has to be position x: 0 <— zero )

Set ‘enabled’ to ‘false’ to turn the monitor off.

Set ‘priority’ to -1 so it is not used as default login display. Maybe you didn’t wanna turn the monitor off but still have the login happen on your Primary monitor?

The bottom half of your file should look something like this:

sudo nano /var/lib/sddm/.config/kwinoutputconfig.json

       "data": [
           {
               "lidClosed": false,
               "outputs": [
                   {
                       "enabled": true,
                       "outputIndex": 0,
                       "position": {
                           "x": 1920,
                           "y": 0
                       },
                       "priority": 0,
                       "replicationSource": ""
                   },
                   {
                       "enabled": false,
                       "outputIndex": 1,
                       "position": {
                           "x": 0,
                           "y": 0
                       },
                       "priority": -1,
                       "replicationSource": ""
                   }
               ]
           }
       ],
       "name": "setups"


Save the file, reboot, then sit back and reflect on a job well done.

When you change your monitor settings from KDE desktop it will create a file of the same name in ~/.config/.

Dont use the Apply Plasma Settings from KDE settings->Colours and Themes->Global Theme->Login Screen (SDDM), it will overwrite the file /var/lib/sddm/.config/kwinoutputconfig.json, though you could edit the file after using ‘Apply Plasma Settings’ once your familiar with how the config works.

BaDboD