First of all, thanks for reading.

I'm running two Nvidia GPUs:

• One GTX 1060 as my primary GPU driving my primary X screen which contains two displays.
• One RTX 2080 as a secondary GPU that I use only for CUDA compute tasks and is not connected to any display. It is, however, driving a second X screen as I like to overclock the card (as far as I am aware, overclocking with the nvidia proprietary drivers is only possible using an X screen).

Here is my X config for your reference: https://pastebin.com/bkqtuteH

The problem I have run into is that when I add this second headless X screen to my X config, KWin gets confused about how to deal with my second monitor. Some oddities:

• I am no longer able to maximise any window on the second monitor. If I click to maximise a window on the second monitor, it maximises on the primary display. Similarly, if I try to fullscreen a video in VLC on the second monitor, it fullscreens to the primary.
• If I have edge tiling enabled and I drag a window onto the second monitor, KWin tries to tile it on the primary display. Here is a screenshot of this (left is secondary, right is primary): https://imgur.com/a/BWfo2Nj
• Occasionally when initiating a window drag on the primary monitor, my cursor will instantly be moved to the second monitor and I will not be able to drag the window back to the primary.

I haven't posted this to KDE bugtracking yet as I'm not certain that it isn't just a mistake somewhere in my configuration. Does anyone have any ideas?