Installing the "Redshift control" applet doesn't automatically install the redshift package, and it's impossible to install it from Discover. Reproducible: Always Steps to Reproduce: 1. Look up "redshift" on Discover 2. "Redshift control" is the only result. Install it Actual Results: The applet is installed, but not the "redshift" dependency. Expected Results: The redshift package should be installed too.
Redshift entry in kde-look is broken as it doesn't really offer any asset to download or install. I'd suggest getting the plasmoid properly packaged by the distributions as there's binary components required. Also the plasmoid should provide appstream information.
@Aleix Pol I installed it from Discover, which I assume doesn't install things from KDE-look. Anyway, that happened only on the Live USB. After installing KDE Neon, I was able to install Redshift too.