Note: I have not done any research on the topic, but I’m just theorizing based on what I already know, as it’s an interesting mental excersice.

Obviously the biggest problems will be uplink and power. Solar and a battery bank is the obvious choice, but other methods of powers can also work, such as a small generator in a river, etc.

Lead acid batteries are relatively cheap, and building a 12V bank out of car batteries makes sense as there is plenty of off the shelf hardware available to invert or transform 12V into whatever you need. Charging it from solar will be inefficient, but it will work, and there is also plenty of hardware for this (tip: boat-related shops can help you out here)

As for hosting hardware we’re of course dealing with the constraints of load vs power consumption. If you can go for something like a raspberry pi zero, you can run for days off of a single car battery with those cheap 5v cigarette-pkug chargers. If you need something more powerful, you need to scale up power accordingly.

As for uplink, the question is “How much” off grid we’re talking. I will assume that there’s at least GPRS coverage that you can connect to with a 4G modem, even if you don’t get 4G speeds. Plenty of off-the-shelf hardware available here. If not applicable, just substitute with whatever is available, be it CDMA, packet radio, starlink (eww), or anything else.