My resolution is stuck at 1024x768 but I use a 2560x1440 monitor. Plasma doesn’t let me change it and there seems to be no way for me to set it to my monitor resolution within Konsole.
I don’t have an applicable display to test with, but you may be able to try kdePackages.kscreen.
kscreen-console --help to get a manual.
I’m not familiar enough with KDE to know the best way to get that to persist across boot; it’s possible just having the package installed is enough for KDE to do its magic—I’m not sure.