I recently did a fresh install of Eoan Ermine, and mounted my old home drive that had been used in another cosmic cuttlefish install. I use two 4k TVs for screens with Nvidia's graphics driver installed. Up to this point,
I also had synaptic run a mass install. *attach synaptic full state file*
The plasma configuration worked well for a few days. I was setting up a new panel with desktop widgets. 
Upon a restart, My panel and desktop were gone, the wallpaper for the bottom TV remained. Right click worked normally. The top tv was black and right clicking did nothing.
I was able to create another panel. When I tried adding widgets, it seemed to be aware of the widgets I'd previously installed. i surmise the initial panel I created somehow got shifted to the top screen and became inaccessible. 



Things I've tried:

I removed nvidia's maintainer 435 driver, installed from the latest .run from their site. Still nothing.  
I moved .config and .kde into a temp folder, but no behavior changed. Should I attempt the same test with .local

Before this black screen cursor issue occurred, I was able to set up options in the Display & Monitor section without having to use nvidia-settings. Subsequent attempts now state no kscreen backend could be found.

Logging in with gnome and xfce work perfectly fine with both displays behaving properly. 

I have always been a fan of KDE but found Plasma4/early 5 to be quite unstable whenever I attmepted to try and use multiple screens. The panel would frequently crash as well. xfce4 dropped their quicklaunch panel plugin.

Workarounds I've thought of:

Run plasmashell or trinity's kicker on top of xfce, and wait until it eventually crashes. 





I am unsure why multiple monitors always causes weird trouble with KDE.