That looks like an interesting device.

I'm more talking about being able to attach a normal laptop to another computer though, without any IP/Networking requirements.

Sipeed has such device https://wiki.sipeed.com/hardware/en/kvm/NanoKVM_USB/introduc...

Cheap 4K HDMI/VGA-to-USB input boards and reverse HID cables are available. Betwen the two for $50 - they turn your laptop into a Moniitor, Keyboard and Mouse for a random computer.

where?