Open Settings
Tap Accessibility
Tap Display & Text Size
Turn on Reduce White Point
Adjust the Reduce White Point slider to a higher percentage
Open Settings
Tap Accessibility
Tap Zoom
Turn on Zoom
Tap Zoom Filter
Select Low Light
Open Settings
Tap Display & Brightness
Turn off True Tone
Turn off Night Shift
Lower the brightness slider to the minimum
Open Control Center and keep brightness at the lowest level
Use Dark Mode
Use a black wallpaper
Enable Reduce Motion
Enable Invert Colors if needed
Use Low Power Mode
Set Auto-Brightness off in Accessibility if you want manual control only