[est]

During China's Xinjiang crackdown people use old fashioned dialup modems and 56kbps is better than 0kbps.

I think if you can still make cross border International phone calls you can setup modem on both sides and create a end-to-end network.

[bobthechef]

I imagine it would be relatively easy to detect that kind of activity.

Maybe some kind of ad hoc mobile/mesh network stands a better chance, though that too is detectable and jammable.