Let’s pull this up. maybe someone will came up with some solution 
Topic summary
Headless Shopify store (custom front end using the Storefront API) needs product links in Facebook/Instagram Shops to point to the merchant’s custom domain (shopname.it) instead of the default myshopify.com subdomain.
- Current behavior: All product URLs in the Meta sales channels resolve to shopname.myshopify.com.
- Attempted fixes: Redirects and other adjustments, but none affected the links generated for Facebook/Instagram Shops.
- Ask: How to configure the base URL/canonical domain used by these channels so that product links use the custom domain in a headless setup.
No technical solution has been provided. A participant notes the lack of answers. The original poster bumped the thread seeking visibility. Status: unresolved; key question remains how to set the custom domain as the link target for Meta Shops in a headless configuration.