We had some SEO analysis software flag that we had missing alt tags on some images.  They were images only found on shopping cart item cards.

The majority of our items have their own product page, and on the product page is athe same photo as also the on the cart card.

The card card images being flagged were only for items that didnt have their own product page where the image had the alt tag assigned.

So the workaround for cart card images that require an alt tag is to create a page for each of those photos with the image on it, with the alt tag assigned..... You can always hide the page, but as long as it is published by the program to your site, the image with the alt tag will get added and the seo analysis software (and google) will be happy.