Is anyone here familiar with Point of sale software? I want to put together a mobile setup equivalent of this: https://youtu.be/G9kfftkWJy8?t=48

Simplified if possible, requiring only to punch in the amount, then for it to display the QR code.

On 1 screen if possible, but could always plug in another mobile screen.

I’m currently investigating and learning it for myself, but this will be quicker if someone is familiar enough with POS software and ETNs instant payment API to walk me through the process step by step, and direct me to anything I’ll need to buy in order to do it.