If you are interested in understanding Stripe API and overall how everything should work with subscriptions you can check out my new course Stripe Integration Course | NoCode Trainer
It is designed to provide all details needed to get up and running and more. The forum post gives more details
It does not cover this exact use case, but you’ll learn more than you would need to know to get it sorted out through the API connector on your own.
BTW my first suggestion was not meant to completely eliminate the need for Stripe Subscription…it was focused on making things setup specifically for AppSumo which as you have explained is different and doesn’t allow for credit card details to be obtained…it is completely possible to have a ‘dual system’ in your application like this.
What is great too is if you have a dual system like this setup and you’ve taken the course, you’ll be all set to notify those users who subscribed through AppSumo to be aware of their subscription expiration and need to sign in and pay for the next subscription year through your Stripe setup.