I have a dual monitor setup using Kubuntu 17.04. The monitors are connected via DisplayPort to the GTX 1080 of my PC. The dual monitors work fine after the login, and their order is correct.
However when I boot up the machine the login screen displays the monitors in the wrong order: i.e. if my mouse is on the left monitor and I try to move it to the right monitor it will be blocked in the middle of the pair of screens. Instead I have to move it to the extreme left to let it wrap around on the extreme right of the pair of screens.
I know how to configure the screen settings, but this seems to only affect their placement after login. Is there some system-wide configuration file that I can use to fix this?
NB: switching the order of the DP cables does not change this behaviour.