it will not work on newer android devices, due to Google's change in allowing access to screen space overlay rendering. sad.
you can root and flash a kernel with K-Lapse , then use a kernel manager app to create your own custom settings according to either available light or time of day.
also some native roms have night shift which is pretty similar to f.lux, just not much control over it.
which phone do you have? and what rom are you running
Update: Try running the app in Virtual space if you don't have root access. (You can try apps like VirtualXposed, Parallel Space, or Dual Space for that)
