I recently found the great utility ddccontrol - which can control different monitor parameters.
My monitor does not have automatic input selection - so, simply turning off the primary input source does no work in my case.
So, I have used it to automatically switch input-source when starting my VFIO Linux VM’s - and switch back when I am done
A walk-through for my Dell U2713HM can be found here: https://glemsomtechs.blogspot.com/2018/07/ddccontrol-automatic-change-display.html
i2c addresses and etc. will need to be changed for other monitors of-course.