So what we’re saying is that a .psbt file can be signed offline and propagated through a mesh (either Wi-Fi, LoRa, or even bluetooth) without a connection to the internet, until it reaches a Bitcoin node?
Discussion
Yes, that would be possible.
If you want to get even more exotic, Blockstream run the Bitcoin blockchain from space.
https://blockstream.com/satellite/
Of course there are offline Bitcoin protocols like e-cash that don't require the Internet at all.
This is honestly impressive, thank you for sharing