start wayland session set breeze dark as your look and feel theme search for "night color" kcm in apps launcher and open it open "Operation mode:" drop down alternatives are listed as white text on white background
Can reproduce Same for: 1. Desktop Behavior - Screen Locking - Appearance - Positioning dropdown. 2. Multimedia - Audio Volume - Devices - Port dropdowns. 3. Multimedia - Audio Volume - Advanced - Profile dropdown. Operating System: KDE neon Developer Edition KDE Plasma Version: 5.14.80 Qt Version: 5.11.1 KDE Frameworks Version: 5.51.0 Kernel Version: 4.15.0-34-generic OS Type: 64-bit Processors: 8 × Intel® Core™ i5-8250U CPU @ 1.60GHz Memory: 7,7 GiB of RAM
*** This bug has been marked as a duplicate of bug 398663 ***