Maybe NIP-32 using ISO-3166-2, with self reporting:
```
{
"kind": 40,
"tags": [
["L", "ISO-3166-2"],
["l", "IT-MI", "ISO-3166-2"]
],
"content": "{\"name\": \"Milan Cats\", \"about\": \"A test channel.\", \"picture\": \"https://placekitten.com/200/200\"}",
...
}
```
