Yesterday I ran updates for the past week. My system had been running well with dual monitors, but when I restarted after the update I had lost one screen, DP-0. When I run xrandr I get this...

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xrandr -q
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
DVI-D-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 527mm x 296mm
   1920x1080     60.00*+
   1680x1050     59.95 
   1440x900      59.89 
   1280x1024     75.02    60.02 
   1280x960      60.00 
   1280x720      60.00 
   1152x864      75.00 
   1024x768      75.03    70.07    60.00 
   800x600       75.00    72.19    60.32    56.25 
   640x480       75.00    72.81    59.94 
DP-0 disconnected (normal left inverted right x axis y axis)


(I'm not using the DVI port on my nVidia card, just HDMI and DP.

When I run Settings, System Settings, Display and Configuration, Display Configuration, it shows just one monitor. The other monitor is working because it's displaying "Plasma made by KDE" and the logo. I can even slide my mouse over to the other monitor but the pointer changes to an X and doesn't do anything else.

Thanks,
RickKW

So, last night while relaxing and watching TV with my wife, I realized I have 3 video outputs on my GPU, HDMI, DP and DVI. I have been using HDMI and DP, not DVI, so why not switch the the monitor on DP to DVI. I did that first thing this morning and it worked. Until I rebooted. Now I'm back to having just HDMI. Xrandr shows HDMI-0 connected, DP-0 and DP-1 disconnected, and DVI is no longer listed. Does anyone know what's going on here? This is all due to updates that I applied Sunday, as everything was working well before I applied the updates.

Thanks,
RickKW

This sounds like my issue:

viewtopic.php?f=66&t=176035

But I haven't heard anything or made any progress on it either...

Hello Grooveman,
Thanks for your post. I was finally able to solve my problem. But first, our issues may be related but there are differences. I have two monitors, HDMI-0 and DP-1, but KDE only showed one monitor, HDMI-0 in Display Configuration and arandr, xrandr and randr. They all showed HDMI-0 and DP-0 with DP-0 as disconnected. When I tried to force DP-1 with xrandr it indicated that DP-1 did not exist. I have an nVidia GTX 1650 and the nVidia console consistently showed HDMI-0 and DP-1, so KDE was just not recognizing DP-1. When I tried to save changes to xorg.conf in the nVidia console I got an error message about absolute screen positions causing display problems, but I couldn't find a way to disable the absolute position.

What I finally did to fix this issue was uninstall, with purge, the nVidia driver (I was at v. 470), and re-install a newer nVidia driver (v. 510). When I rebooted, the problem was still there, KDE still didn't recognize DP-1. I checked xrandr and Display Configuration, no change. I opened the nVidia console and now for the first time since this issue started I had a Position button with Absolute and various other positions. I set my left monitor (HDMI-0) to Absolute +0+0, and my right monitor (DP-1) to Right of. I was able to save that to xorg.conf. I rebooted and the problem was gone. Now the nVidia console still shows HDMI-0 as Absolute +0+0, but DP-1 is now Absolute +1920+0.

To replace the nVidia driver you should first backup critical just in case something goes wrong. then open a console and enter these commands...

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apt list '*nvidia-driver*'

sudo apt-get purge '*nvidia*'

sudo apt install nvidia-driver-510

I chose the nVidia 510 (not server) driver only because I don't like to be on the latest driver with nVidia.

Hope this helps

RickKW