Created attachment 168444 [details]
take a look at the bottom of the screen

SUMMARY
I have a 16" laptop with Plasma. With 100% scale due to the big screen resolution, everything is too small to read. Even Plasma itself set scale to 150% by default. In this case I see either colored glitches in the form of dashes at the bottom edge (always) or sometimes it's just a white line at the bottom of the screen (rarely). Sometimes the white line at the right edge of the screen (very rarely).

It looks like hardware screen issue. Well it could be. But when I set scale to 100% in KDE there is no issues at all.
When I try Fedora with gnome live usb I don't see glitches even with scale up. When I installed Windows for update UEFI reason I also didn't see glitches.

Unfortunately, I sold out my old laptop but I'm recalling kind similar behavior there but less noticeable (can't prove again)

STEPS TO REPRODUCE
1. Go to Settings --> Display configuration
2. Set the scale up to 150%
3. Open in full screen size mode image or video player or similar. It's better to observe on the black background

OBSERVED RESULT
On the bottom and sometimes on the right side of the screen I see just a few pixels width artifacts (glitches)

EXPECTED RESULT
Without glitches?

SOFTWARE/OS VERSIONS
OS: Arch Linux x86_64
Kernel: 6.8.4-hardened1-1-hardened
Display (BOE0AC1): 2560x1600 @ 120Hz (as 1280x800) [Built-in]
DE: KDE Plasma 6.0.3
WM: KWin (Wayland)
WM Theme: Breeze
Theme: Breeze (Light) [QT], Breeze [GTK3]
Icons: breeze [QT], breeze [GTK3/4]
Font: Noto Sans (10pt) [QT], Noto Sans (10pt) [GTK3/4]
Cursor: breeze (24px)
CPU: AMD Ryzen 7 7840HS with Radeon 780M Graphics (16) @ 6.08 GHz
GPU: AMD Phoenix1