Can I show recommendations on checkout pages?

Frequently Bought Together allows adding a checkout extension to show recommendations before proceed to the payment. This feature is available for app Professional plans. However, take into account that due to a current Shopify restriction this kind of extension is allowed only for Shopify Plus stores.

See https://docs.codeblackbelt.com/article/2492-how-to-add-a-checkout-extension for more info.

The checkout is not the only place beyond the product page: recommendations can also be displayed on the cart page. See How many widgets are available and where are they displayed?