India's UPI is also extremely quick and easy to use - instant transfers with just the person's phone number or via a QR code or via a UPI id which looks like an email id. We are talking about 19-20 billion transactions per month. Apart from UPI, there are other interbank transfers methods such as NEFT, IMPS, RTGS etc. All quite convenient and easy to use.
In some setups UPI doesn't even internet! Just an SMS is sufficient
RCS might work as it's a bit more secure (and more importantly: doesn't have a 2G/3G compatible version that criminals might trivially abuse); it even has an optional money sending API in its protocol.