If you are referring to the KDS or CDS feature between two iPads, that does not require an internet connection. You only need a Wi-Fi router to provide that functionality. The internet is what allows the apps to sync their data to the cloud environment. We use Loyverse without internet all the time, it’s one of the things that appealed to us.
Quick note. Wi-Fi is often defined as Internet but that is inaccurate. Wi-Fi is a local network connection. Think of Wi-Fi like your house with several rooms. Each room is connected inside the house. To reach the outside (internet) everyone leaves their rooms (pc’s) to go out the front door (internet connection). If you close the front door (internet down) you can still walk around your house (local Wi-Fi connectivity).