SUMMARY
When I use a Dell U2913WM (2560 x 1080) external monitor with my Dell XPS laptop, a 1 pixel wide strip of the display that should only be on the laptop monitor appears on the edge of the external monitor.

Callout: The big problem that this causes is when I ask KDE to bring to up the "Present Windows - Current Desktop" overview (which I have set as a Desktop Effect->Screen Edge trigger in Settings) all windows from both screens appear - making this hard to use (otherwise this 1 pixel wide strip would not be a big problem).




STEPS TO REPRODUCE
1. Log into KDE
2. Plug in external monitor - it will likely work fine (callout: set the external monitor to display to the right of the laptop monitor if you want to get the same test conditions as me)
3. Sleep KDE
4. Wake KDE (the resolution on the external monitor may come back on okay - or it may not; if you repeat this step a few times it likely will come back wrong eventually, though I can't be sure what the exact condition is that trigger it. I get this issue every day however)
5. If the resolution on the external monitor is wrong then plug out and plug back in the monitor
6. If the resolution is correct proceed to step 7. If not try step 5 again
7. Usually, if the resolution comes back correctly there will be a 1 strip wide pixel down the left of my external monitor (that is likely from the laptop display)

OBSERVED RESULT
A 1 strip wide pixel down the left of my external monitor

EXPECTED RESULT
No 1 strip wide pixel down the left of my external monitor

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Ubuntu Studio 22.10
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.98.0
Qt Version: 5.15.6

ADDITIONAL INFORMATION
Kernel Version: 5.19.0-1018-lowlatency (64-bit)
Graphics Platform: X11
Processors: 20 × 12th Gen Intel® Core™ i9-12900HK
Memory: 62.5 GiB of RAM
Graphics Processor: Mesa Intel® Graphics
Manufacturer: Dell Inc.
Product Name: XPS 15 9520