Shopify Storefront Web Components Not knowing when checkout complete event happens

I’m using Storefront Web Components, on one of our non shopify sites (non theme). On that site we have a ordering flow that is in a step by step process. First introducing a product, then user is able to use the web-component checkout using shopify checkout popup modal. Once the checkout completes though, the web components specifically the cart doesn’t clear, and there is no way of knowing on the frontend where the web components are placed, that the user made a payment, and move them on to next steps, and instruct them about their order.

Was originally using the shopify buy buttons - Buy Button - Add Your Products to Any Website - Shopify
But with the update to thank you/statue page on checkout it no longer works the same way, as before. Where when checkout is completed after making the order. buy button components some how know.

Need a way for frontend to know when a checkout is complete.