I didn’t have much issue with the previous monitor I had but my new one is not going fully to standby mode. It works fine on Windows (dual-boot).
I have a Philips PHL 246E9Q connected to my laptop via HDMI. When it tried to put the monitors into sleep the laptop screen turns off fine but the external monitor will attempt to go to sleep (screen will go black and message saying no signal, going to sleep mode), but just as the monitor goes to sleep it wakes; The laptop screen and monitor come back on. Sometimes the laptop screen will go to sleep but the monitor never does.