Several years ago, Apple introduced its adaptive color temperature feature “Night Shift,” while iOS 13 includes system-wide Dark Mode.
These features are designed to change the temperature and color of your display based on what time of day it is. New research suggests, however, that features designed to reduce blue light before bedtime might not be as effective as initially thought.
I never accepted what F.lux did on Mac before Night Shift was conceived and I haven’t used the latter since it was introduced. I also have no trouble falling asleep, even while holding my iPad and reading. I do like Dark Mode though — it’s so much easier on the eyes.