I'm confused, why do you want hardware and what do you want the hardware to do? And, why not use a USB keyboard?

You could use an rpi pico. It has a usb port and there is a software hack to bit bang a second usb port, iirc.

I am wondering if connecting over USB is an XY problem.

To try and clarify a bit: I am essentially trying to have a KM (KVM without the V) over USB.

To go one step higher, I am trying to control a mac mini from the keyboard of a macBook.

	▲	brudgers 9 days ago \| parent [-]
		Why not use the macs’ built in “sharing” functionality?