Change "Continue Shopping" URL on Thank you page (Headless)

[Seppiee]

My current issue is that I am using the Headless channel of Shopify. I am querying products and other data through the Storefront API and have an entirely different Frontend as the shop. 

However, we still use the default Shopify Payment flow for checkout, and that all works fine except for the very last "Thank you" page, this contains a Continue Shopping button that redirects the visitor to the storename.myshopify.com, how can I adjust that Continue Shopping link so that it redirects to my custom Frontend instead?

We are not using Shopify Plus, so the Checkout UI components seem to be out of the question; also the Additional Scripts support seems to be deprecated and will be entirely removed end of april 2025. Does anybody know what to do?