I've published a NIP-17 event with the key in the nostrsdk-debug repo, and now REQ receives that event from auth.nostr1.com So there were probably no events published for that key on that relay

I've checked this but I can't reproduce the issue. I've tried both the auto-auth implementation and the manual one, and both successfully send the REQ after the AUTH and receive the EOSE. To debug the messages that the client send, you have to enable the debug level: "RUST_LOG=debug cargo run" You must enable the "env-filter" feature for the tracing-subscriber dependency, to be able use RUST_LOG

The URL in the AdmitPolicy is to let you know from with relay the AUTH request is coming. You don't have to add it, it's added by the SDK.