I usually only use it via command line, but that’s disappointing to hear that it’s no longer supported. I have used redshift-gtk in the past but I could never keep it functioning for very long, and I prefer KDE. It seems every alternative wants to automate it to synchronize with sunrise and sunset, but 90% of the time I use it is simply because my eyes are already aching. I wish there was another with an easy access on/off switch. The built-in functions require going into settings each time I want to change it and that’s just no good.