Fix kde scaling issue with arch and nvidia on Macbook Pro with external monitor
Manually set the dpi. Edit...
sudo vim /etc/X11/mhwd.d/nvidia.conf
Add to "Screen"...
Option "UseEdidDpi" "False"
Option "DPI" "96x96"
Making something like...
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Depth 24
Option "UseEdidDpi" "False"
Option "DPI" "96x96"
EndSubSection
EndSection
From: https://forum.manjaro.org/t/nvidia-proprietary-driver-ui-scaling-issue/38204/6