Since Apple's iOS 10.0.2 it is possible to operate iOS devices via USB-LAN adapters without WiFi in a network.
1x Lightning to USB Adapter
1x USB to LAN Adapter
1x Lightning Charging Cable
The Lightning to USB Adapter is a passive adapter. This means that it does not emit energy to connected devices. A Lightning charging cable is therefore absolutely necessary to power the iOS device and the USB to LAN adapter.
Check which network is used in WLAN, e. g. our network of 7 (ROM, MAILAND...)
So it is not allowed to use the 7th network for ethernet, otherwise you have either no internet or it doesn't print.
Here is a recommendation that we tested:
The entry Router and DNS can be skipped if the network is not extended via ethernet.
Lightning to USB
USB to LAN Adapter