With the implementation of Commit 3b06b6f2 (Improve appearance of text selection), on some screens it is difficult to distinguish the selected text. There doesn;t seem to be an option for the amount of the color difference between selected and not selected text.
KDE Frameworks 5.81.0
Qt 5.15.2 (built against 5.15.2)
KDE Plasma Version: 5.21.4
The change in question:
*** This bug has been marked as a duplicate of bug 435309 ***