As you may know, Shopify recently released a new checkout version called Checkout Extensions UI and we're glad to let you know we now support both checkout.liquid and the new Checkout Extensions UI.
The instructions are slightly different for each version, please go to the App Dashboard > Address Prompts > Instructions
After you do that, you can see our installation process which is now easier than before since you don't need to modify your code. Read more about the Checkout UI Extension Integration here.
The new Checkout UI Extension Integration offers the same functionality as the previous checkout.liquid version in terms of address validation, however, there are still some limitations when it comes to customization and the prompts. Now the prompts are embedded instead of the previous window pop-up. We will add more functionality as Shopify releases more APIs.
(Please note pop-up windows are only available with checkout.liquid at the moment)