Bug 407461

SUMMARY
Running on Kubuntu unstable CI, as of about two weeks ago, the CTRL+` (Key_QuoteLeft) cannot be assigned to any global shortcut. When trying to assign it, it appears to be set correctly but when invoked - the specified function does not activate and instead a notification pop up shows up with the last desktop notification.

STEPS TO REPRODUCE
1. open the Global Shortcuts configuration dialog
2. Select some function and configure it to be triggered on CTRL+`
3. Press CTRL+`

OBSERVED RESULT
A KNotifications popup appears showing the last notification displayed and possible a timer showing how much time has passed since the notification was originally displayed. Additional triggering of the shortcut shows additional notifications up to 4.

EXPECTED RESULT
The configured global accelerator should have triggered the specified function.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 5.15.80
KDE Frameworks Version: 5.58
Qt Version: 5.12.2

ADDITIONAL INFORMATION
I don't know what component takes over this shortcut, and without involving kglobalaccel - as I didn't find any configuration in the global shortcuts dialog that uses CTRL+`, nor did I get a conflict notification when I try to set it up, so I'm posting this to kglobalaccel as an act of desperation ;-) I've reviewed KNotifications source code and I don't think it is responsible for this.