I saw how this application (Cardiograph) uses a bright flashlight, and then it switches to a dim one. The phone itself (Samsung Galaxy A10s) does not have a built-in flash brightness control, and there is no root either. So, how can you adjust the power of a flashlight, what applications are there for this (maybe even somehow through Termux)? Samsung Galaxy A10s phone, Android 11, all updates installed.
Video
/sys/class/leds/
. None is guaranteed to work on all devices. Except that the OEM or custom ROM developer has already added the option in Settings.