JbakTaskMan has a torch using the screen. Unfortunately it leaves the red LEDs on. Open the lens cover until they they turn off. Then close it.
BrightLight uses the white LEDs and it's brighter. Run it. Close it. Run it again then light comes on. To turn turn off - close program, rerun and quickly exit. If left on the LEDs get hot. If you turn off and on the phone, then you need to run the app twice before the light turns on. After that only one time is needed.
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Tools>Settings>General>Personalization>Themes>Power saver>Date