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
Research NDI. It transports video with embedded audio via Ethernet. You can capture screens via software (NDI Tools is available at NDI.tv)