First of all, please make sure that "Storefront filtering" is enabled and configured as described in this tutorial: How to enable the “Storefront filtering" option? (powered by the Shopify Search & Discovery app)
Then enable the Universal products option: (Go to EasySearch → Scroll down to the “Universal products” section → click “Settings” → switch the “Enable universal products” toggle):
Use the “Add Products” button to assign the universal products. Please don’t forget to save the changes once done.
