I'm somewhat concerned by the laid back attitude of the quote from our fearless leader mentioned by Laura above.
What Rick is quoted as writing is
It’s a good idea to get one if you’ll be driving in Austria,
Bosnia-Herzegovina, Croatia, Greece, Hungary, Italy, Poland, Romania,
Slovenia, or Spain — countries where you’re technically required to
carry a permit,
That seems to me to be a very uninterested description of a law. "Technically required"? It is the law, binding on all foreign drivers from outside the EU+EEA. It isn't "a good idea" any more than "it is a good idea to carry your state drivers license" when driving in the US.