Linux installation and correcting the 404 Not Found Error

[Pitone_Maledetto]

From scratch:
sudo add-apt-repository ppa:nathan-renniewaldock/flux
sudo apt-get update
sudo apt-get install fluxgui

If you already had it but you get the following on sudo apt-get update:
W: Failed to fetch http://ppa.launchpad.net/kilian/f.lux/ubuntu/dists/ trusty/main/source/Sources 404 Not Found

sudo rm /etc/apt/sources.list.d/kilian-f_lux-trusty.list
sudo add-apt-repository ppa:nathan-renniewaldock/flux
sudo apt-get update

[DeadPhysicist]

1. Do we know why the original source went down and if it's going to come back up?
2. Are you associated with this project somehow? I don't feel comfortable putting an unknown source into my trusted sources list...

[Pitone_Maledetto]

I don't know why is not maintained anymore by Kilian but the original GIT repository provides the link to the project discussed above.
Old GIT:
https://github.com/Kilian/f.lux-indicator-applet which links the new maintained one at:
https://github.com/xflux-gui/xflux-gui

If you have any concerns you could always remove the source and don't update the application.
No, I am not associated with the project.
Hope it helps.