Trying UPI (Unified Payments Interface, the instant payment system in India) for the first time feels, in its present state, like a poster child for federation with all its benefits and drawbacks. It’s not clear at first glance that some clients/banks are interoperable, but things seem to work together a bit better than you would expect if you can get past that confusion. To be fair, I’d be glad if Matrix/ActivityPub were more widely used and client UX was the biggest problem we had.