I bought a cheapo capture card a while back but the quality is pretty terrible
Is there any reason PCs can’t just receive HDMI/displayport input from other devices through the same mechanism they output it?
For that matter also is there any reason HDMI can’t be run over Ethernet? Afaik ethernet has far more bandwitth than hdmi nowadays
For your video output question, essentially the PC has a card that is capable of saying what the monitor needs to do, and ths monitor has a card to translate what the PC said into the screen output. The PC doesn’t have the card that the monitor has. It isn’t equipped to receive picture signals.
And kinda…technically…uh… you can run video signals over Ethernet. You just need the protocols to communicate between them, and the ports to connect them (would you sacrifice wired internet for a video signal for most desktop boxes?). Other elements are cost, compatibility, design. I’ve seen that some TVs have Ethernet and fibre-optic ports now.