KDE Plasma: System Settings black menues on black background

I installed KDE Plasma Workspaces on RHEL 8 and I love it! But I have a strange issue, where in System Settings GUI I don’t see menu options on the left side bar. All is black. But when I hover the mouse then they appear as a separate box on the right then disappear when I move the mouse away:

Any help will help :slight_smile: