Here's a neat little bitcoin decoder for transactions, lightning invoices, vtxos, and nostr -- all in one place. You can run it on your own device, but it will still fetch into from public servers, so be sure to follow the steps to point at your own node and nostr relays if you are worried about leaking your own personal data.

Most decoders run fully offline, but transaction lookup (opts.transaction.fetch) and Nostr profile fetch (opts.nostr.fetchProfile) hit third-party servers by default (mempool.space and public relays).

Your IP and the queried txid/npub leak to whoever runs them. Pass opts.transaction.endpoint / opts.nostr.relays to point at your own infrastructure if that matters.

From the things I looked up, the interface is very neat and clean.