@aeva you could probably Frankenstein together something with one or more active adapters but this is not trivial.
The short version is that VGA/DVI/HDMI are all basically locked to the dot clock for a virtual CRT that, at this point, usually does not actually exist and needs HBlank, VBlank periods to retrace the electron beams.
And then extra data (such as HDMI audio) is transmitted over the signal pins during the blank periods.