UK. I haven't used or carried cash here for about 3 years. Other than a really inconvenient time someone gave me some for one of my kids and I had to pay it in.
UK again. Almost all shops accept both cash and debit/credit card. So you can survive without cash, but you can also survive without digital payments. Though they might not be the sort of people who visit this web site, I see lots of people paying with cash in shops. Occasionally you see a small business or a temporary set-up that only accepts cash or only accepts cards -- they typically have a notice apologising for the inconvenience -- but you could just avoid them.
However, if one private person is selling something to another private person, and they don't know each other, then it's nearly always cash because most people aren't set up to receive digital payments, don't want the hassle of setting it up just for one odd item, and in any case wouldn't trust the technology and companies involved for a large sum so people quite frequently pay for a second-hand car in cash if it's a private sale.
Luckily, cash is still a majorly accepted payment method over here from my experience. I did my weeks food and charity shop shopping all with cash on the weekend. Markets are still very accepting of cash as an example. We have options still but for how long, I'm not too sure but hopefully indefinitely.
However, if one private person is selling something to another private person, and they don't know each other, then it's nearly always cash because most people aren't set up to receive digital payments, don't want the hassle of setting it up just for one odd item, and in any case wouldn't trust the technology and companies involved for a large sum so people quite frequently pay for a second-hand car in cash if it's a private sale.