It worked, when I tested a kaos iso about a year ago. Currently I don't run Kaos a a Qemu/KVM guest.
I encountered the same problem first with Openmandriva
and got no solution. Furthermore I have the issue with Fedora 31 as guest (host is also Fedora 31), whereas installations of Mageia 7 and Mageia Cauldron work fine.
I have another issue which is clearly KDE/Plasma related. Copying text from konsole into the clipboard fails, whereas it works with other desktops as Gnome or Xfce. I see my VMs as test, not productive installations. So I gave it up, did not want to waste further time on the issue.
@Mtncaos: Do you have a better display when you go to fullscreen mode?
Edit: Retested. Screen resolution works now with upgraded Openmandriva Lx 4.1. It fails still with Fedora 31.