How to power off display on inactivity?

I have the latest CoreELEC running on Odroid N2
It is connected to a projector which does not seem to be supporting CEC.

I quite often fall asleep while watching something and I would like for the projector to turn off when the film ends, to save the lamp.

Unfortunately, since the projector does not seem to support CEC, the only time it would shut down is when there is no signal on the HDMI input. I tried the ‘Blank’ screen saver, but it just keeps running on it.

So my question: is there a way to turn off the HDMI output upon inactivity?

I found this screen saver add-on, that would be ideal for my needs, but it does not work:
It just does nothing instead of turning off the display.

Is there any command line tool that can turn off the display output?