How can I configure a free shipping discount for all the bundles?
Once inside, check the 'Apply a global discount to all Frequently Bought Together bundles' option and select the 'Free shipping' discount type:
Then, on the left side, you can configure the minimum bundle amount to apply discounts (zero if you want the discount to apply to all bundles). On the right side, you can also configure the discount message that will be displayed in the Frequently Bought Together widget. If you want to configure the styling of the discount message, it can be done in the 'Visual preferences' section.
The discount won't be displayed on the shopping cart page (this is a Shopify limitation). To overcome that, you can configure a message that will be displayed on the cart page when a discount is applied. You can configure the message, its position and styling, in the 'Visual preferences' section. For more information, check the related document 'Why are discounts not displayed in the shopping cart?'.