Stripe supports no-cost orders in the latest version of their API, which as far as I understand it, doesn’t ask for a payment method when a purchase or subscription is free.
This can be configured in Stripe > Settings > Checkout: Stripe Login | Sign in to the Stripe Dashboard
More info here: Kostenfreie Bestellungen | Stripe-Dokumentation
I would like to request that Softr adds support for no-cost orders so that Softr users aren’t prompted to enter a payment method when their purchase/subscription is free.