Ah. Yup. You need to disable a few hotkeys at the system level.
So, and pardon this, this is from memory as I haven’t been in front of a Linux machine for a long time, but what you are looking for is the place to turn off system-specific hotkeys.
Try something like:
System Settings / Keyboard and Mouse / Global Hotkeys …and then, I think there’s a pull down menu there with options…you are looking for…umm… I think KHotkeys or KWin. Somewhere in there is the Print Screen and Scroll Lock hotkeys that you want to disable at the OS level. Also, Control-ESC is somewhere around there as well. Disable those and Fran’s your Nan.
(and, hope you don’t mind, I adjusted the name of the topic to be a bit easier for others to find in the future)