Unfortunately I don't use a note 9, however depending on what features you're trying to turn into a dark mode, some apps have a built in dark mode option in their settings. What you could also do is install a different home launcher (my go to is Nova Launcher). Also for more customization such as a different lock screen and even routines such as enabling the blue light filter at a certain time, install Good Lock from the Samsung app store and the side apps within it.
One would think, in the never ending search for more battery life, and Samsung's predominantly Super AMOLED panels on a vast majority of their phones, that they would push hard for system wide Hex Black "theming" ..
It may not be huge, but the Hex Black pixel requires no power to be black. So having So Much White, just seems to be counterproductive when battery performance is so important in the market...
I have a Galaxy 7 star. Cheap purchase of 79.95 with new account, but now a freebie with Metro PCS. I have found in a few themes, after the mostly dark front screen, all other search screen are mostly black. The app. buttons are lighter, but I search free only. Maybe being some what ignorant in diagnostics of cell phones, I may have misunderstood the question. I check weekly, delete often and I have one now that I have loved weeks! I found a rare total red without images around 3 months ago. I keeping it stored, until my provider decides to delete while I sleep. I update nightly.