Puzzle date
Hint 1 · Continent
Europe.
Hint 2 · Land borders
Finland, Russia, Sweden
Hint 3 · Capital
Oslo.
Reveal the mystery country
Norway
How we verified this answer
The official Globle client reads an encrypted country index from its daily response and looks up the country in its own list. The record includes that response and both official client files.
Also confirmed by completing the official round with the browser set to Pacific/Auckland.