I just tested this on my dual monitor setup, Nobara Linux, KDE Plasma version 6.5.2 running Wayland and it worked no problem.
Set my main monitor to 150% scaling and left my side one to 100%.
Now on my setup, both monitors are 1080p, although my side one is oriented vertically, so Idk if it would act different if I had one at a completely different resolution.
Edit -
I just tested it on one of my laptops running Linux Mint Debian edition 7, (Debian 13 Trixie under the hood) with the Cinnamon desktop environment running X11 and it worked perfectly also. 4K TV set as the primary monitor scaled at 150%, the laptop’s screen as the secondary, 1080p at 100% scaling, applied the settings and it was completely fine.















“Yes, I’m sure I typed my password correctly.”
Working in IT, I can’t tell you how many times I’ve heard that and how many times it’s been wrong.