I am building digital content selling app for ios using flutter like music etc. I have used stripe payment gayeway but app store has rejected it. It says we can only use IN APP PURCHASE for it. Is there any solution for this?
Digital content purchases for both Google and Apple are controlled by them. You have to use Google Play Billing and Storekit. Both companies will then facilitate the payment from the client and take their cut, remitting the balance to you. There is no way around this if you want to use their app stores.
Physical or services purchases can use eg. Stripe because the app stores allow that.
The package referred to by the other answer simply makes it easier to implement the necessary code in your app. There are others such as the one from Revenuecat.