you probably don’t want the instance admins handling your payment info

Unfortunately centralized (but I don’t think it’s possible to do that with the traditional banking system due to gateways) but it’s actually very easy to integrate with Stripe.com , as you to integrate yourself might be a day of work at most (source : I did few integration with WebXR as prototypes) but if you, as a self-hosted admin of the platform instance, just want to make it work, you probably only need a working account (to receive the actual money) and you’d fill up only IDs and voila, working.

Now there is also the KYC challenge, not sure how that work as a platform intermediary. Honestly at that point, as someone else suggested with Belgium 2ememain.be better letter user handle that themselves and in Europe with IBAN it’s pretty trivial to pay online, no fee.

Might also be worth exploring https://developer.mozilla.org/en-US/docs/Web/API/Payment_Request_API

any advice or suggestion, please do give

I haven’t build one so I can’t help as much… but I’d be honest from the start by comparing it, head-on, with alternatives (if I understood correctly) e.g. https://github.com/searxng/searxng and simultaneously, because it’s federated, make it interroperable with them.