Interesting article in the New York Times today, echoing what many people have said in the forums. Hurried along by the pandemic, the cashless economies of Europe are becoming the norm. It recounts the story of an American traveler from Michigan who, no matter how hard he tried, could not spend the 700 British pounds he brought along. Even outside of London in the Lake District and Cotswolds, many restaurants would not accept cash. They finally used the cash to pay off their hotel bill after the hotel "let" them so they wouldn't have to covert it back to USD. Experts in the article advise travelers to be prepared to tap, not swipe or insert the chip, as many vendors only accept contactless cards. Check your card for a series of four curved lines on the card to verify it will work for contactless transactions, and if it's not there, call your company for a replacement. Along with this admonition, travelers are also advised to check the foreign transaction fees, as it could cost you up to 3% of every purchase.
The article suggested that the traveler has a digital back-up plan, for example Google Pay or Apple Pay should your card not work.
On the other hand, in Portugal and Malta recently, we found that some cash was handy for tips, small shops and restaurants. Keep some change for pay toilets. Learned that one the hard way....