This is just the PCB and pre-soldered PS2 & RJ9 sockets and a socket for the Arduino, you supply your own Arduino Nano V3 clone, regular RJ9 phone cable, and flash the Arduino yourself, no soldering required. Full version here https://www.ebay.co.uk/itm/167145739930

It didn't work with genuine Mac USB keyboards, or a Compaq PS2, or wireless USB keyboards that I tested.

It worked fine with 3 fairly recent cheap sub-£10 keyboards I tested.

Don't be tempted to power the Arduino externally, it will make no difference and might kill your Mac.

I also tried using an Arduino Uno clone board instead and that made no difference to which keyboards work or don't.

I mention all this so you shouldn't feel the need to try it...

The RJ9 phone handset cable this design uses is standard wiring and shouldn't be used with a real Mac Plus keyboard - you would kill it. You can see the adapter working in the attached video.

Any Nano V3 clone should work fine. Make sure you set the Arduino software to Arduino Nano (Old Bootloader) in boards menu on correct com port. Will include download links with the PCB version.