I came across these answers, it explains in detail suggestions on how to do it.

In UNA, PayPal (including “PayPal API Client ID + Secret”) is not inherently “operator-only”—it depends on which seller mode you’re using and which profiles are allowed to act as sellers.

How UNA is designed

1) Site owner / “Main Seller” (operator/site admin use case)

UNA’s Payments app has a “Site administrator” (seller) concept used for site-owned monetization like Paid Levels, donations, etc. That profile is effectively the platform’s seller account. ()

2) Individual members as sellers (multi-vendor use case)

UNA supports members selling (courses/products/etc.). In that case, each member who plans to sell must configure their payment provider in the user-end settings:

Account → Settings → Payments (where they can enter PayPal / PayPal API credentials). ()

So: Yes, multiple users can each install/configure their own PayPal API Client/Secret—but only if they are operating as sellers on your site (i.e., they have access to the Payments settings and selling features).

Marketplace / Market App specifically

UNA’s Market app is integrated with the Payments app. If you want to sell items in the Market, you start by setting up Payments, and sellers then configure providers on the user end. ()

Who “receives” the money and commissions

• In a multi-seller scenario, payments can be associated with the seller profile (the member) after they configure their provider. ()
• For taking a cut/commission, UNA’s community guidance describes approaches such as the Payments app Commissions feature (monthly summaries/invoices) or “Single Seller” mode (you receive funds, then pay sellers), and an alternative via Stripe Connect (more complex). ()

Direct answer to your question

• Can all users install PayPal API Client/Secret and receive payments?
• Only users who are allowed to be sellers (i.e., have access to user-end Payments settings and selling functionality). It’s not “everyone by default,” but it’s also not limited to operators. ()
• Is it for the Marketplace/Market App?
• Yes—Market uses Payments, and seller/provider configuration is part of enabling members to sell. ()

good luck with your project.