SUMMARY STEPS TO REPRODUCE 1. Plug in an external display (hdmi), and have a different taskbar on both screens. 2. Turn on "Show only tasks from the current screen" 3. Unplug the external screen OBSERVED RESULT The task manager is empty on the laptop screen EXPECTED RESULT Task manager should show all opened applications as there is a single screen now. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch Linux (available in About System) KDE Plasma Version: 5.17.5 KDE Frameworks Version: 5.66.0 Qt Version: 5.14.0 ADDITIONAL INFORMATION If KDE is started with a single screen, the task manager does show all tasks. The problem appears only when the display is removed. I think there is some state kept where the system thinks there is still another screen, even though the display settings shows a single one. It is 100% reproducible on my system. (The external display has a higher resolution, the taskbars are vertical.)
*** This bug has been marked as a duplicate of bug 414743 ***