Hello There!
We would like to inform you that you can the Payment Gateway from Stripe to Paypal for your existing Customer through the Upgrade/Downgrade Subscription option by creating an Offline Payment through the Payable Invoice.
For this you have to add the Paypal payment Gateway to your Plan for which you want to take payment through Paypal. Then Go to the Subscription and Select Upgrade/Downgrade Subscription option after that Click on Offline Payment / Create Invoice option in Payment Method.
Then an Payable Invoice will be generated which you can share with your customer through the sharable link (Invoice Section) on which there will be mentioned different Payment Gateways which you have added in your Plan. Once the customer made payment through Paypal then Customer's Card will get registered in Paypal then from the Next payment the Charges will deduct automatically through Paypal.
Hope the above information helps you.
If you need further support please reach out to us.
Regards,
Vipin Mishra