The user signs up for paypal, gives a public wallet address for bitcoin, etc and then you're helping them manage a payment screen?
It could work, but what has struck me about LinkTree is that the users are non-technical (I think). Anybody with the desire could easily set-up a webpage and host their own list of links. LinkTree is saving them from doing that, and for somebody who is on insta, youtube, etc, but without their own personal website, LinkTree gives them the ability to quickly send users to their other platforms.
If this is an opportunity in the billing space, good on you, this could work. However, for non-physical goods, Patreon, etc is already providing a billing platform.
If you are selling physical goods, you're probably using Shopify or something similar which already has a billing platform.
So who is the customer who does not have a platform where they are selling their goods, and therefore need a diverse list of payment methods.
I rarely use PayPal because I can't stand the company (I moved a lot internationally for a while, and they would keep blocking me from using their service, massive PITA).
For most people, doesn't PayPal serve the need, and Venmo in the US (not Amerrican, so don't know).
I'm not going to say it's a bad idea. I think it could be very good, but do you know the answers about who your customer is?
I'd also mention that since launching the app, I have see the users span from basketball coaches, non-profits to side hustlers.
You might want to read my full reasoning here https://paylinkz.app/about
I'm finding that clearly describing some of the users it is for can help people understand how they would use something.
Awesome work.