There are several projects now to fetch data from the ring without subscription and display it in self hosted apps.
No, we want an offline solution directly from the ring. It doesn't seem like anyone has managed to get around needing it to call home at least once to initialize. That still requires an app install and a subscription to get started. Nobody is buying these secondhand for cheap and then truly and completely bypassing the official app.
This project is the closest I've found to doing it properly, but you still need to extract the key after initialization before ditching the official app and subscription.