Stripe SCA is a refactored version of the standard Stripe payments to update the Stripe API to v3 and support the SCA process flow. Other than using different Stripe API calls to set up and process payments, the main change is to defer order fulfillment to a web hook called by Stripe after the payment has been authorised.
This module is installed as a separate payment method from the standard Stripe module and can be run in parallel.
Note that it shares the customer_stripe_tokens table created by the standard Stripe module, and cards saved using the standard Stripe module can be reused by the Stripe SCA module, however, cards stored by the Stripe SCA module cannot be reused by the standard Stripe module. They will be rejected by Stripe with a message 'You cannot create a charge with a PaymentMethod. Use the Payment Intents API instead.'
For both install and updates, the contents of the install folder can simply be copied to the catalog folder of your web site, or the root if osCommerce is not in a catalog directory.