It’s quite a common fact that these run Linux. They’re everywhere, and sometimes one can see them on “system information” with Linux specs. Who knows if they can be hacked or cracked open. Models typically have a few hundred MB of flash, and up to a few hundred MB of SDRAM.

https://www.verifone.com/en/us/mpos

https://www.verifone.com/en/us/countertops-pin-pads-multilane