SUMMARY

Pinned Firefox Nightly icon at task manager will create a second Firefox (stable) icon when started, instead of the task being associated to already pinned icon.


STEPS TO REPRODUCE
1. Pin Firefox Nightly icon to task manager (drag and drop Firefox Nightly icon from menu launcher to task manager);
2. Start Firefox Nightly by clicking over its task manager pinned icon;
3. Firefox Nightly will start and a new separated task icon will show up at task manager;

OBSERVED RESULT

- Starting Firefox Nightly from pinned icon will generate a new task icon in task manager while Firefox Nightly is running. This new icon is orange and not blue (it is associated to Firefox Stable, and not Firefox Nightly).

- Trying to pin Firefox Nightly to task manager (right click over current running instance of Firefox Nightly) will pin Firefox Stable instead of Firefox Nightly.


EXPECTED RESULT

- Pinned Firefox Nightly icon, when started, should not create a new task icon at task manager. Firefox Nightly task should be associated to the already pinned icon.

- Pinning Firefox Nightly from right click over currently running Firefox Nightly task should pin Firefox Nightly icon and not Firefox Stable icon.


SOFTWARE/OS VERSIONS

Linux: Arch (Linux 5.11.14-arch1-1)
KDE Plasma Version: 5.21.4
KDE Frameworks 5.81.0
Qt 5.15.2 (built against 5.15.2)
The wayland windowing system


ADDITIONAL INFORMATION

This behavior seems to have been introduced very recently, somewhat in Plasma 5.21.x, but may be triged by some Firefox update, I'm not sure.