SUMMARY There's a setting where the laptop isn't put to sleep when the lid is closed. In this case the display should be disabled as we can't see what's in there. STEPS TO REPRODUCE 1. Connect laptop to an external display 2. close the lid 3. nothing happens OBSERVED RESULT The step 3 should be "the display gets disabled and the workspace doesn't span to the closed display". EXPECTED RESULT SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
Works well for me as long as I first uncheck the "Even when an external monitor is connected" checkbox in the powerdevil KCM.
I can confirm it works, was hitting another issue.