Czech Republic. Usually my girlfriend has ~$5 on her for stuff like lemonade stands or public bathrooms, and I'm the irresponsible one who hasn't carried cash since 2018. Some pubs, very small stores or small tourist attractions (climb a tower, see the inside of a church, etc) are still cash-only, especially in the rural parts of the country, but visiting or living in Prague (the capital) cashless is easy with zero issues.
I believe so (not entirely sure), but there’s a mobile app now and a new kind of machine where you just tap your card and out comes a pre-validated ticket that you can put in your pocket and ride. The regular ones that need to be validated are a trap for unsuspecting tourists.