I never realized my own design was compatible with them too!
https://pinside.com/pinball/machine/undertale-pinball-edition
I wonder how they hook up? There are no standard system plugs anywhere on the game, so my guess is it has a dedicated power supply that you plug into the duplex outlet inside the cabinet. You'll have to pull out one of the existing plugs, so you can take your pick on what feature to disable - the playfield voltages, or the computer!
Edit: I also applaud them for their understanding of UT's electronics. I was pretty sure I built a playfield controller that takes direct inspiration from the System 11 boardset, but I see that they recommend the Stern version. I guess I was wrong!