SUMMARY
The activitiesChanged signal is not emitted, when the window is not present on the current activity.

STEPS TO REPRODUCE
1. Use this code in kwin script:
    client.activitiesChanged.connect(() => {
      console.log("ActivitiesChanged is called")
    })
 
2. Move window to another activity via Alt+F3 menu

OBSERVED RESULT
The window disappears from the screen (moved to another activity), the log is empty

EXPECTED RESULT
The window disappears from the screen (moved to another activity), the "ActivitiesChanged is called" is printed.


SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.86.0
Qt Version: 5.15.2
Kernel Version: 5.10.69-1-lts (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-8550U CPU @ 1.80GHz
Memory: 15,5 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 620

ADDITIONAL INFORMATION

The log message is printed only if we change activities, while keeping the window on the present screen.