> I see that a lot of people are unaware about UPI on HN, I might summarise my experience in a separate post and comparing it to Zelle

Please do! I would buy you a coffee or similar for doing so. Likewise if someone wants to create and maintain a Wikipedia page listing instant payment systems and their details (because FiServ keeps taking down their marketing enumerating this information while also excluding it back from Wayback Machine[1]), I'd be willing to throw some fiat at that.

[1] https://www.fisglobal.com/en/flavors-of-fast (404s, don't bother clicking, Modern Treasury has some content marketing that refers to it)