It is possible to have access to WiFi without an actual internet connection. Having access to WiFi allows for local communication between a printer and an iPad. So the printer and iPad are able to communicate tasks via a local area network (WLAN) without having an internet connection.
Recommended LTE routers
LET Routers that can keep WLAN (local wireless network) active if there is no internet connection
Huawei CPE2 Pro
NetGear NightHawk M1
Windows Mobile Hotspot
*A workaround in case you are using Windows 10 for printing
*This is not an official Snappic printing solution but just a last resort
Windows has a feature where it allows the internet connection to be shared using a local Hot Spot and in some cases, it can be used as an iPad hotspot when using a Venue WiFi and it doesn't allow printing as it then bypasses the main WiFi router and all the venue Firewalls.
On your laptop press Start/Settings/Networks/ then on the left side, there will be Mobile Hot Spot, Once you enable the Hot Spot Connect the iPad to it and it should print.
In case you have any additional questions, please let us know on the Live Support Chat