I live in a remote area too and have to use this work around. It's 2020 we should be able to update with confirmation over cellular just as we do with large apps.
Connect your iPhone to your Mac via usb cable and turn on hotspot on your iPhone under settings and then go to your Mac and click on the Apple logo / system preferences / sharing / choose internet sharing and share your iPhone usb hotspot connection to the WiFi and turn it on by checking it. Then go to your iPhone and choose the shared WiFi from your Mac and you'll be able to update over WiFi.![]()
A ghetto hack that works is not a ghetto.