Hello, These two keys do not cooperate. Ctrl + Right works as in standard word processor and moves the cursor one word forward but Ctrl + Shift + Right does not select the content as it moves. Shift + Right selects the character as the cursor moves forward letter by letter but Shift + Ctrl + Right keeps moving letter-wise not word-wise. Browser story: Ctrl + Tab moves focus to the next browser tab, Ctrl + Shift + Tab continues in the same direction (should go reverse). It seems both Qt and Gnome applications are affected: libreoffice, kate, firefox.
Did you select the 'QtCurve' category by accident, or did you verify that the issue is only visible when using this style engine?
Made a guess. How to verify?
Please check the active widget style via 'kcmshell5 style'.
The active widget style is Breeze. Then I should file this bug somewhere else regarding keyboard input.
For anyone's reference, there was a conflict between the keyboard layout change mechanism (Ctrl + Shift) and the normal use of these keys in applications. Changed the keyboard layout change sequence to something else and the symptom is gone. Still it shouldn't interfere, it worked fine in Kubuntu 16.10 and before.