Created attachment 158207 [details]
Bug video

SUMMARY
Firefox window shown multiple times on each monitor. Please find the video attached.

STEPS TO REPRODUCE
1. Open Firefox on a PC with 2 monitors attached

OBSERVED RESULT
Firefox is shown on both screens in overview effect. Other effects like Present windows/Grid also affected.

EXPECTED RESULT
Firefox is only shown on single monitor

SOFTWARE/OS VERSIONS
Operating System: EndeavourOS 
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.105.0
Qt Version: 5.15.9
Kernel Version: 6.2.11-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 24 × AMD Ryzen 9 3900X 12-Core Processor
Memory: 15.5 GiB of RAM
Graphics Processor: AMD Radeon RX 580 Series
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: X570 AORUS ELITE
System Version: -CF

ADDITIONAL INFORMATION
The issue is only reproducible with Firefox. This is a fresh OS install.
Using latest Firefox nightly 114.0a1 (2023-04-18) (64-bit)  (.tar.gz)
Firefox Desktop file:

[Desktop Entry]
Name=Firefox Nightly
X-GNOME-FullName=Firefox Nightly
GenericName=Web Browser
Comment=Browse the Web
Exec=/home/shubhamarora/Applications/firefox/firefox %u
Icon=/home/shubhamarora/Applications/firefox/browser/chrome/icons/default/default128.png
Terminal=false
Type=Application
MimeType=text/html;text/xml;application/xhtml+xml;application/vnd.mozilla.xul+xml;text/mml;x-scheme-handler/http;x-scheme-handler/https;
StartupNotify=true
StartupWMClass=firefox-nightly
Categories=Network;WebBrowser;
Keywords=web;browser;internet;
Actions=new-window;new-private-window;

X-Desktop-File-Install-Version=0.26

[Desktop Action new-window]
Name=New Window
Exec=/home/shubhamarora/Applications/firefox/firefox --new-window %u

[Desktop Action new-private-window]
Name=New Private Window
Exec=/home/shubhamarora/Applications/firefox/firefox --private-window %u