I am trying to learn about the enode concept, the node addressing system that Ethereum clients use
I seem to recall in passing that Ethereum transaction propagation has some degree of privacy because the nodes don't know they were the first node to see the transaction, or who the first node was, but nowadays I can't find any literature on this as the wallets have abstracted all this away and people rely on services like Infura or Alchemy to propagate transactions through their load balanced fleet of nodes. The load balancer seeing everything about the sender's IP address and offering no privacy.
On a fundamental level, what do nodes see and record? Do they know where an unconfirmed transaction came from?
On UXTO blockchains, the nodes know exactly which node say a transaction first and information about who sent it.