Hello,
I have 4k laptop and a secondary monitor which is 1920 x 1080 and I was wondering if there is any way to change scaling of this monitor on its own. I’m aware of the global scale option however this wont work because of big difference in scales between screens. Also I know that it should be possible using xrandr but I was hoping there would be painless gui way to do that.
I’m using x11 if that’s relevant.
We only support per-monitor scaling on Wayland. If you figure out a way to do it on X11, that’s up to you 
It was a surprise for me
But, unfortunately, if I select anything except 100%, text at the second display looks blurred.
My external display is not large: HP Z24n G3
You need to reboot afterwards. This limitation comes from Qt and is already fixed fir Plasma 6.
You could set the resolution of the 4k display in Display Settings to something smaller, e.g. 1024x768, to have a somewhat similar scale to the external monitor. Could come with the cost of unused black areas at the side.
For X11, see this post for a DIY approach.
Sorry for reviving, but this seems to be the most recent topic …
… and this is only “my trick” to come along with it.
I run a 2k left and a 4k on the right.
Put the scale in the system settings on 200%.
bash commands:
FIRST scale the smaller one 4x4:
$ xrandr --output DP-0 --scale 4x4
THEN run the “proportions”:
$ xrandr --dpi 276 --fb 7680x2160 --output DP-0 --mode 1920x1080 --scale 2x2 --pos 0x0 --panning 3840x2160+0+0 --output DP-1 --mode 3840x2160 --pos 3840x0
Don’t ask me why first scaling down and then up again, but for me this works fine and is exactly the result I need.