Software update

An intentional design feature of iOS/iPadOS requires that an OTA system software update is conducted over a WiFi connection. You cannot use the device’s own Cellular connection - as the Cellular Radio is itself updated during a software update; the update process requires a robust network connection to reliably perform the update and (re)activate the device.

The alternative update mechanism is to use a PC or Mac computer to perform the update over USB. Whilst a network connection is still required to complete the update process, this method removes reliance upon the stability of WiFi (or Cellular) network connection to the iPad during the update process.

When you are using a non-Apple WiFi hotspot connection, you are fooling the device into believing that it has an adequate network connection. In so doing, you are at the mercy of the reliability of the Cellular connection during an update process; if the process fails, your device may be non-functional until such time at the OS is completely restored by either a PC/Mac computer with a network connection - using iTunes or Finder as appropriate for the computer that is being used.

If you are away from a “reliable” network connection, performing an OTA system software update is relatively high risk - exposing you to the possibility of losing use of the device pending restoration. If you are “at sea”, you would be well advised to avoid attempting system updates until you are within range of a robust network connection.

You don't, sorry.

A wifi connection is mandatory to update an iOS device.

If you don't have one, "borrow" one from your neighbours, go to a pubblic place with wifi capabilities, or ask for help in a shop selling electronics or some service provider.

Regards

Giulio

As an alternative, I'd try to use an Mi-Fi device (I use an old TP-Link M7350, which is always with me when I'm away from home, for secure and fast wifi connection with internet access for my iPhone and other 9 devices).

I'd give it a try.

Regards

Giulio