Hello, i recently bought a cabinet that had, what appears to be, a very old i-pac ps/2 controller in it. This particular version does not look like the one on the website here:
https://www.ultimarc.com/control-interfaces/i-pacs/i-pac-2-classic-ps-2-version

The page above doesn't exist - the site shows an error for a missing page.

It does not look like that. The model in my cabinet has two ps/2 ports on opposite ends. They are labeled PC and KBD.

Question is will retropie support this old ipac controller via a ps/2 to usb controller? And if so would I follow the programming instructions here?

I'm not sure, but if the IPAC identifies as a keyboard and it works without additional drivers, then it should be ok - RetroPie (or Linux rather) can use the keyboard.

@dorkvonwaterfall my IPAC4 has the ps/2 plug, but he wire I have adapts it to USB. You could always email Andy at Ultimarc and see what limitations you have. If you can use USB via the right cable, it’s a great interface. It is keyboard only and you won’t run into problems with it accidentally being detected as a gamepad.