flux overrides xrandr
I use ubuntu 1804 on my laptop.
I can't use xrandr while f.lux is running, f.lux sets all settings back to:
$ xrandr --output LVDS-1 --brightness 1
I want to dim screen brightness while flux is running... this way it would be much easier to read... during the night.
I think you should reInstall an alternative Operative System after formatting your HD/SSD (hard drive or solid state drive).
After this, try and download f.lux in your clean new OS.