One aspect of no phone is how to deal with payments. Specifically UPI payments in India. These are QR code based payments and it is getting more difficult to pay by cash at many locations.

Right next to that is OTPs from financial institutions.

On the way towards the same issue in Vietnam. You can still pay with cash everywhere but it's becoming more and more normal to use QR codes. I guess in the next year or two I'll start to see places that only take QR. It's very convenient... unless you don't have a local bank account, or your phone runs out of battery, or, as happened to me 30 minutes ago, your bank's system goes down.