Install flux on linux:
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sudo add-apt-repository ppa:nathan-renniewaldock/flux
sudo apt-get update
sudo apt-get install fluxgui

from: https://github.com/xflux-gui/fluxgui

Origonal date in Vivaldi: 
7 March 2018 @ 21:43
Note: This may date back to 2017 but everything was lost in early 2018.