Bug 472578

Created attachment 160503 [details]
Dual monitor desktop -- 2nd monitor is displaying BLACK ... But screenshot shows a desktop.

SUMMARY

When I restarted the workstaiton the second screen no longer displayed as a desktop extension.  A power-off and restart cycle had no effect.  I am pretty much stymied now because I need both monitors to perform several essential activities.  Trying to use just one screen will really curtail productivity.

Everything worked just fine before the system shutdown.

Also I ran the "Display and Monitor" system settings pressing 'Detect" did not display on the 2nd screen, the cursor displays.  So I can see that the hardware is fine.  In addition, I made the second screen a mirror of the first screen with the "Replica of" setting; the second screen came-to-life showing a clone of the Primary monitor.

Turning the replica off however left me with a black screen.

This appears to show several symptoms in common with earlier bug: [#450068](https://bugs.kde.org/show_bug.cgi?id=450068) and its duplicates.  

STEPS TO REPRODUCE
1. I do not know what happened, the monitor was 'gone' after a restart.

OBSERVED RESULT

NO second monitor -- I have attached a  screenshot of the two screen set-up.  When you look at the screenshot there is a second monitor desktop showing.  I do NOT see that.  I only see a black monitor and the cursor is displayed as it moved in that part of the viewport.  May be there is a clue in that screenshot???  I actually expected half of the graphic to be black!

EXPECTED RESULT

* Expect it to work as it has done since I installed Plasma/Kubuntu on this PC back for 21.10, it has worked absolutaly fine for dual monitor case.

* Expect some easy to find documentation to say where to look in the configuration files to determine what a normal multi monitor set-up should look like.  Obviously the Display and Monitor gui does not tell the whole story.  In fact once I saw that the "Replica of" setting showed me that the second monitor worked fine in both esoftware and hardware, I discovered it is non-trivial to get the extended display setting back (ie. No Replica).  

* I also think and "About" box could have a tab to say where to find critical elements like:
    * Relevant config files
    * Relevant log files
    * Link to things like troubleshooting wiki page or commands that might be useful in documenting or understanding what is going on.

SOFTWARE/OS VERSIONS

Linux/KDE Plasma: 
Operating System: Kubuntu 23.04
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8
Kernel Version: 6.2.0-25-generic (64-bit)
Graphics Platform: X11

Hardware
Processors: 16 × AMD Ryzen 7 2700X Eight-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: llvmpipe
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: B450 AORUS PRO WIFI 

ADDITIONAL INFORMATION

* Attached information

    * Window manager - KWin
    * X-Server
    * syslog (since reboot)