Supercharger auth is between the car and the charger and doesn't require an internet connection. I get billed the normal way via my Tesla account since the VIN is registered
There's some functionality loss but it's mostly been mitigated. I have a custom app I wrote since I can't use the stock app.
The one feature I miss is that there's no voice commands since that requires Tesla's servers but at the same time I also haven't been bothered enough to plug in a custom backend
It’s ok, the voice commands are barely understood anyway. At least in the UK they aren’t. Gets it drastically wrong and messes up your navigation destination, because you asked it to open the glovebox “navigating to Columbia”