The attached patch detects if dark mode is enabled on Windows (10+)/macOS (10.14+) at server start, and styles the runtime accordingly. It doesn't dynamically switch if the user changes their preferences.
Linux builds continue to use the standard styling from Qt.
NOTE: I've tested this on macOS, but my Windows build system is playing up at the moment. Akshay, can you have someone on your team test it please? I believe the code should work; it's just a case of reading a reg key and then doing the same thing as on macOS to set the theme accordingly.