Again, thank you for your reply.

>if you are in a such remote area that you can't even run a mobile LN node

It is not a thought experiment about a node being in a remote area. To the contrary. It is a thought experiment about where exactly the "edge" of the network even is, whether we can safely push lightning and lightning payments out to the edge. 

But I suppose I did not spell it out that way and can understand how you interpreted it.

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As I said, if you are in a such remote area that you can't even run a mobile LN node like Breez, Blixt, SBW, Nayuta, Electrum... I don't know why do you want to complicate so much.

If you are in a such remote area, you will not have anyway where to spend your bitcoins, not even online. You will be more focused on shelter, water, food, security than... internet and bitcoin.

bitcoin

thought experiment: how to keep full node in sync without traditional internet?

As I said, if you are in a such remote area that you can't even run a mobile LN node like Breez, Blixt, SBW, Nayuta, Electrum... I don't know why do you want to complicate so much.
If you are in a such remote area, you will not have anyway where to spend your bitcoins, not even online. You will be more focused on shelter, water, food, security than... internet and bitcoin.