SUMMARY
When using two monitors (in my case, laptop's internal monitor + external screen), the activities switcher menu does not display when the main screen is not leftmost. When clicking the activity switcher icon in the KDE panel, the current window loses focus, but no switcher appears either on the main or on the secondary screen. When the main screen is to the left and extended rightwards, everything works as intended.

STEPS TO REPRODUCE
1. Attach additional monitor.
2. Set screen configuration such that the main monitor is rightmost, the desktop extended to the left.
3. Click on the Activities switcher icon on the panel.

OBSERVED RESULT
The activities switcher does not appear.

EXPECTED RESULT
The activities switcher should appear on the left edge of the main screen, regardless of the multi-monitor setup.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Aurora-dx 41 (from Fedora Kinoite 41), kernel 6.13.8-200.fc41.x86_64
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.13.0
Qt Version: 6.8.2

ADDITIONAL INFORMATION
This used to work as expected in earlier versions of Plasma 6, but I cannot report the exact version when the regression happened.

Since the current window loses focus when clicking on the activities switcher button, the cause of the bug is probably that it tries to display the switcher on the leftmost edge of the desktop, which happens to be on another screen (but for some reason does not appear there either). Instead, the switcher should appear on the current screen.

This is similar to what was reported as bug 452165 for "add widgets", but it was fixed a long time ago. For the record, this bug only applies to the activity switcher. "Add widgets" and other sidebars work as intended.