(Quick-note) Troubleshooting Dual Monitor Issues on KDE on Ubuntu/ Linux Mint

TLDR

Learn how to troubleshoot and resolve issues with dual monitors on KDE, especially when one monitor stops working or remains off.

Context

By default, KDE handles dual monitors well on a new installation. However, sometimes one monitor might stop working and stay off. This happened to me, and I had to fix it using xrandr and KDE's display settings.

Steps

Here is how I resolved my issue:

1. Run xrandr Query :

xrandr --query

This showed two activated displays.

1. Copy Display Names : I identified display names from the xrandr output.

❯ xrandr --query
Screen 0: minimum 320 x 200, current 5120 x 1440, maximum 16384 x 16384
HDMI-A-0 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
2560x1440144.00*+ 120.0099.9559.95
3840x216030.0025.0024.0029.9723.98
1920x1200144.00
1920x1080120.00119.8860.0060.0050.0059.94
1600x1200144.00
1680x105059.88
1280x102475.0260.02
1440x90059.90
1280x96060.00
1280x80059.91
1152x86475.00
1280x72060.0050.0059.94
1024x76875.0370.0760.00
832x62474.55
800x60072.1975.0060.3256.25
720x57650.00
720x48060.0059.94
640x48075.0072.8166.6760.0059.94
720x40070.08
DisplayPort-0 connected primary 2560x1440+2560+0 (normal left inverted right x axis y axis) 597mm x 336mm
2560x144059.95*+
1920x120059.95
1920x108060.0050.0059.9430.0025.0024.0029.9723.98
1600x120059.95
1680x105059.95
1280x102475.0260.02
1440x90059.89
1280x96060.00
1280x80059.81
1152x86475.00
1280x72060.0050.0059.94
1024x76875.0370.0760.00
832x62474.55
800x60072.1975.0060.3256.25
720x57650.00
720x48060.0059.94
640x48075.0072.8166.6760.0059.94
720x40070.08
DisplayPort-1 disconnected (normal left inverted right x axis y axis)

1. Execute Command :

xrandr --output HDMI-A-0 --mode 1920x1080 --right-of DisplayPort-0

I set HDMI-A-0 as the main display, right of DisplayPort-0.

1. Adjust in KDE Preferences : I went to Preferences > Display Configuration. I set the desired resolutions and applied the changes.

2. Fix Overlap : When there was overlap, I changed both monitors to a lower resolution, applied changes, then set the preferred resolution again.

Following these steps fixed my issue, and both monitors worked correctly.

References

• KDE Display Configuration
• xrandr Documentation