SUMMARY
Latest KDE on Arch Linux (September 4, 2021) has all notifications misplaced, they are shown with a small offset below the mouse cursor. They should be always on the right bottom corner.
Attached 2 screenshots from my dual-screen setup that show notifications on random places below the mouse cursor (Spotify + Spectacle notification triggered)


STEPS TO REPRODUCE
1. use any application that uses desktop notifications
2. you will see that the notifications are all misplaced


OBSERVED RESULT
you will see that the notifications are all misplaced

EXPECTED RESULT
They should be always on the right bottom corner (default corner)

SOFTWARE/OS VERSIONS
Windows: N/A
macOS: N/A
Linux/KDE Plasma: 5.22.5 on kernel 5.13, latest arch linux + all updates
(available in About System)
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.85.0
Qt Version: 5.15.2
X11

ADDITIONAL INFORMATION
X11