I have 2 out of 3 monitors orientated 90° clockwise. However when I designate them as such in System Settings➝Display and Monitor I get upside-down display. The workaround to get proper display is to lie and designate them as orientated 90° _counter_-clockwise. Shutting down KDE, deleting ~/.local/share/kscreen/* and rebooting does not fix the issue. I found similar bug 335211 fixed in the past…
This problem still exists in plasma 5.12.0
Still reproducible in Plasma 5.17 or the 5.18 beta?
No, kscreen 5.17.5-1 on Arch seems to get it right.
Oh good!