An LTE dongle would still require a cell data subscription. Have you considered a dedicated hot-spot device with subscription?
You don't need internet during flight though. You'd only use it to confirm there's no firmware updates and to update the map shown in the app. The app caches what it already gathered for the map so you don't have to continually have internet.
Even then these are optional.
I guess I am not understanding your need. Any device such as your normal daily device/phone would be good enough for the 2-3 minutes of hotspot to accomplish what you said your use is for, then power down hot spot and no more battery consumption. A use such as that would be a weeks worth of HotSpotting on a battery ...but perhaps this thread from DJI site can help: Anyone tried plugging a 4G USB A dongle into the smart controller
Why do you want a hotspot when you can download caching your maps prior go to the field?
It’s been done. But where did DJI state that last I heard they said it is not compatible.So DJI state that the SC can use a usb lte dongle for internet connectivity.
I want to avoid using my phone as a hotspot as it keeps disconnecting.
Which dongles are compatible ?