MarsSeed  filed a deletion request for fluxgui :
Project added warning in 2020 that most likely this
won't work or won't properly work with modern systems.
Lack of screen adjustment was reported as early as 2016 with Linux
Developer recommends that people user RedShift instead.
My addition to that: major desktops like GNOME and KDE
have already added night light dimming / yellowing of the
screen. So this originally Windows application is
not needed now on Linux. Most people don't even need to
install anything nowadays for such functionality.
I think trying to fix this application is not worth the