Here: https://github.com/Shopify/product-reviews-sample-app/blob/main/docs/checkout-extension-post-purchase.md#8-enable-the-extension
It says that
By default, extensions are not enabled for online stores, we’ll need to change our store’s setting to use our new extension.
So, this would require the merchant to manually enable the extension from settings.
I was wondering if there’s a way to do this via API, so that extension gets automatically selected when the app is installed.