SUMMARY I've had this problem at least since kf5 5.38, plasma-workplace 5.10.5, Fedora 25. Now on kf5 5.54, plasma-workspace 5.13, Fedora 28. I disable Klipper. The clipboard will just stop working, or work erratically, in my main KDE apps: KMail, KAlarm, Konqueror, Konsole. The clipboard doesn't seem to get populated by a KDE Ctrl-C/X, or highlighting. Ctrl-V or middle-click pastes whatever non-KDE app did a Ctrl-C/X or highlight. Seems like KDE disconnects from its own and the X clipboards. I had to use Chrome to file this bug report because Konqueror does NO copy/paste. STEPS TO REPRODUCE 1. In a KDE app, Ctrl-C/X or highlight 2. In any other app, KDE or not, Ctrl-V or middle-click OBSERVED RESULT Whatever a non-KDE app left in the KDE/X clipboards is pasted. EXPECTED RESULT Whatever was Ctrl-X/V or highlighted into the clipboard should be Ctrl-V or middle-click pasted. SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: 5.13.5 (available in About System) KDE Plasma Version: 5.13 KDE Frameworks Version: 5.54 Qt Version: 5.11.3 ADDITIONAL INFORMATION This behaviour seems to coincide with windows opening in the background, e.g., when I opened KInfoCenter from the K Menu to check versions it opened minimized to the Task Bar.
> I disable Klipper. But why? Klipper was written to prevent the issue you are seeing.
You need to use a clipboard manager like Klipper for this to work. That's the whole point of them. :)