I am developing a mobile app where users can create works of art for purchase. In order to download the completed art, the user must purchase the artwork. The artwork is then downloaded as a PNG to the user's device. The image can only be used outside the app. The downloaded artwork cannot be used inside the app. Should I use Google Play's billing system or my own (such as Stripe) for the purchase?
According to this answer, I should not use in-app billing for my app because it's not allowed
where payment is for digital content or goods that may be consumed outside of the app itself (e.g., buying songs that can be played on other music players).
However, I cannot find any reference to this in Google's documentation.
I chatted with their customer support, and they told me they can't help with me "technical support for app development questions" and should I refer to the documentation.