The UPI experience is built for a single audience in mind. It has changed the way people transact in India but at the same time it's been an absolute nightmare for a tourist to play along. The only route for a tourist to use UPI is via third party apps, which charge a markup for loading money (3%). But let's say you accept that as a part of travelling - the limitation of tourist wallets is that they can't be utilised for P2P payments - exactly what UPI is most used for across the country.
Alternative, since no one accepts cash anymore, is that I have to carry thick wads of cash so I can hand out exact change. That still gets you the stink eye because most vendors don't like to deal with cash anymore.