It sounds like you’ve done quite a bit of research already, and unfortunately, PayPal's current SDK doesn’t natively support user-to-user payments within an Android app. The Adaptive Payments API, as you mentioned, was a solution for this use case, but PayPal has deprecated it and now encourages newer approaches. If you’re looking for alternatives, you could consider using PayPal Payouts (sending funds from your app's account to a user’s email) or exploring other platforms like Stripe Connect or MangoPay, which are designed for P2P payments with smoother in-app integrations. For a more tailored solution, you might need to develop a custom P2P payment app. I found a detailed guide on how to create p2p payment app that explains the steps and technologies you’ll need to consider.