SUMMARY Alt+Tab hides all windows on the other screen when switching between windows on the current screen. STEPS TO REPRODUCE 1. Have two monitors attached 2. On the first screen: open at least one window 3. On the second screen: no windows open 4. In System Settings / Task Switcher settings: Filter by screen when switching with Alt+Tab. 5. Move the mouse pointer the to second screen 6. Press Alt+Tab and release. OBSERVED RESULT Nothing should happen. EXPECTED RESULT The window on the first screen is hidden. SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: 5.26.4 (available in About System) KDE Plasma Version: 5.26.4 KDE Frameworks Version: 5.101.0 Qt Version: 5.15.7 ADDITIONAL INFORMATION
Thank you for the bug report! Please note that Plasma 5.26.4 will not be supported for much longer by KDE; supported versions are 5.27, and 5.27 or newer. Please upgrade to the latest version as soon as your distribution makes it available to you. Plasma is a fast-moving project, and bugs in one version are often fixed in the next one.
At the moment the behavior is intentional. You can disable this behavior in System Settings > Window Management > Task Switcher > Uncheck "Show selected window" if you don't like it.