With VGA, it was simple: duplicate the EDID to both inputs, switch the output wires, done. AFAIK, with DisplayPort it's not so simple, since there is a negotiat

With VGA, it was simple: duplicate the EDID to both inputs, switch the output wires, done. AFAIK, with DisplayPort it's not so simple, since there is a negotiation between the computer and the display, including link training (see https://lwn.net/Articles/736011/ https://lwn.net/Articles/736011/ for instance). IIRC, HDMI also has some bidirectional communication. To work well, a KVM would have to act as a display to the computers, and as a computer to the display, instead of just passively switching some wires.