Just back from a week in Slovakia using a USD-denominated Visa card via Apple Pay. Most cafés and restaurants charged EUR without any messing about, but supermarkets (Billa and Tesco chains) and one restaurant made me choose a currency after tapping my phone (F1 or 1 for USD, F4 or 4 for EUR).

At that stage, the POS terminal did not show me any information about the exchange rate, final amount or additional charges I would incur if I chose USD. For obvious reasons, I didn't proceed further to find out.