Asus PG279QM Monitor Backlight Stays On in Standby

How to turn the backlight off in sleep mode

The PG279QM is an excellent gaming monitor. However, there was always something that annoyed me. When the monitor turned off and went to sleep mode, the backlight stayed on for at least 2 minutes.
In a dark room this was quite noticeable.

The solution is to disable Input Auto Switch. This way the backlight will turn off after only ~5 seconds.

It remains unclear why the backlight stays on while the monitor is searching for input signals from HDMI/DisplayPort but if you don’t need the automatic input selection try this workaround.