This is the difficult and expensive part:

Now we need to listen to all the broadcast Nostr messages from many of the popular relays which support empty subscription_id values, thus allow us to receive all messages broadcast on the relay.

This can then be uplinked to satellite, either directly using a modem, BUC and paid for satellite bandwidth, or through an intermediary such as Blockstream Satellite https://blockstream.info/.

That, with the receiver network, gives us an 'off grid' darknet, that does not require Internet access in order to transmit or receive messages. With transmission performed via HF radio, and reception through a satellite dish. Of course the Internet is still used to forward messages.

However transmission is somewhat anonymous, and reception is totally anonymous.

Giving us a network, that for reception, is far more secure than Tor, because it's physically impossible for receivers to be traced or located in any way.