Do Paypal and Bitcoin work as standard payment processors for applications in the Play store? And Amazon, for non-Kindle devices? The whole point of the walled

Do Paypal and Bitcoin work as standard payment processors for applications in the Play store? And Amazon, for non-Kindle devices? The whole point of the walled garden is that, in order to be able to access a customer base, you have to play by the rules of the gatekeeper (and pay the toll). I'm not comfortable with a market model where the only choice is what garden you want to be in.