But yet, Night Shift works just fine on my Dell U2412M. Toggling Night Shift on/off using the switch in the Notification panel (right side) shows the Night Shif

But yet, Night Shift works just fine on my Dell U2412M. Toggling Night Shift on/off using the switch in the Notification panel (right side) shows the Night Shift effect just as it does on the built-in display on my Macbook Pro (late 2014).