Can you also check KRun, I'm sure we've had issues with startup reporting stuff in the past

You mean if there are such calls?
Can do.
Btw., Gwenview doesn't render for me any pictures on the second screen either, but I found there no suspicious code :/

For KRun for me the calls there look properly guarded.

Can I merge this? The effect is quiet "evil" here ;=)

If possible I would like to have this in 5.63, as otherwise any color scheme change will make all Qt applications on the non-primary screen unusable with scaling.

If nobody objects will push that later, without any window on secondary screen is garbage after palette change.

It would be great to have that in 5.63, or I am too late?

Done, this is in the v5.63.0-rc3 tag now.