SUMMARY
The context menu for files located on the desktop on the primary screen in my dual screen setup always appears on the secondary screen.

This is how it looks like:
https://grzesiek11.stary.pc.pl/files/images/Screenshot_20210619_212453.png
https://grzesiek11.stary.pc.pl/files/images/Screenshot_20210619_212515.png

STEPS TO REPRODUCE
1. Create a new file 'primary.txt' on the primary screen.
2. Create a new file 'secondary.txt' on the secondary screen.
3. Open the 'secondary.txt' file context menu (right click).
4. Open the 'primary.txt' file context menu.

OBSERVED RESULT
'secondary.txt' has it's context menu properly located on the secondary screen, but 'primary.txt' context menu opens on the secondary screen too.

EXPECTED RESULT
'secondary.txt' has the context menu on the secondary screen, 'primary.txt' has it on the primary screen.

SOFTWARE/OS VERSIONS
Operating System: Debian GNU/Linux 11 (Sid)
KDE Plasma Version: 5.22.1
KDE Frameworks Version: 5.83.0
Qt Version: 5.15.2
Kernel Version: 5.12.0-11.1-liquorix-amd64 (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Core™ i5-2400 CPU @ 3.10GHz
Memory: 11.7 GiB of RAM
Graphics Processor: GeForce GTX 660/PCIe/SSE2

ADDITIONAL INFORMATION
My secondary screen is 'VBIOS primary' or something like that (I don't know the correct term) - BIOS POST and GRUB show up on it, and TTY resolution is adjusted to it too. I don't know if this matters.