I have a system with 2 4K displays, an HD display and an HD drawing tablet running Ubuntu 24.04.2 with X11, plasmashell 5.27.12 and KDE frameworks 5.115.0
This has been running for a few months.
Today I tried to change my display setup to clone the HD (1920x1080) display to one 4K display, and scale the display using nvidia-settings such that the 4K display got downscaled on the drawing tablet.
I couldn’t get either nvidia-settings or Configure Display Settings to save settings across a reboot. I also had problems where the non-KDE applications including QT applications displayed properly but applications like Konsole and any systems settings panels had text that was about twice the correct size, aong with widgets in those programs.
I got my system back to a state where my non-KDE applications are displaying like they used to.
However, I cannot get KDE-based applications display configuration to reset to what they were, even changing global scaling in display settings.
If I knew what file I had to edit this to reset the scaling for KDE applications or what file(s) to delete so my system could reconfigure itself, then I can fix this.
Suggestions?
Thanks
I found that if I set global scaling to 125 in Configure Display Settings, then desktop icons, text in windows like the configure display settings, window titles are back to close to their original sizes. But then anything that is not a KDE app seems to be scaled up 125% which I don’t want either.
I did a recursive grep in ~/.config looking for the value 125 and didn’t find it. So it’s either not there or the display settings converts it to something else, either way, I have no way to figure out how to fix my display settings.
Also, if I change the global scaling to 100%, which is the lowest possible value, then I’m back to where I was where icons, etc are way too big.
Hi! I’m not an expert on handling multiple monitors or drawing tablets, so I’d defer to others for ideas on your specific situation…but as a general note, X11 is going to be a bit funky with fractional scaling at different levels on different devices.
Needing to have multiple displays scaled at differing levels is a common use case that would drive trying out a Wayland session. I will also say that the Plasma + NVIDIA + Wayland experience has gotten a lot better in Plasma 6, so if you’re up for trying new distribution versions, either Kubuntu 24.10 or a more generally up-to-date distribution might be worth trying out for the improvements when running such a setup 
I tracked this down to in part the X11 configuration, and tried a couple suggestions to fix that but it seemed every time I logged out or rebooted my displays were all mis-configured in different and un-amusing ways.
I just found plasma-workspace-wayland and installed that. I tried a few of the programs I use on a regular basis and they at least seem to basically work correctly. So I’ll see how well Wayland behaves for me. Maybe it’s finally to the point where I can ditch X11 which is really ancient software.
Thanks