I’ve not worked directly with any of these payment systems, but I can’t believe the only solution is go all 90s style Windows based system. There will be embedded ways that comply to regs.

I can see they are Windows based when there is issues. I’m sure of Tesco and Morrisons but Sainsburys I don’t go to often enough to have see an issue that bring up Windows. I was being flippant, but I don’t hold using Windows to build stuff in high regard. In my experience the software engineers who doing that don’t know anything else.