By default, the same description will be used for both Desktop and Mobile devices. Our standard eBay template is mobile-optimized, so this usually is not an issue.
However, there are scenarios where the description HTML in Shopify causes the listing to lose its mobile optimization. If so, you can specify a mobile description as follows:
Single Edit mode (listings tab)
In your eBay listing click on Mobile Description, enter the text, and Save
Bulk Edit mode (listings tab)
Scroll to the right and look for the Mobile Description column, click the Edit link, enter the text, and Save
Any product that has a mobile description will now use this for mobile devices.
For further assistance, please reach out to firstname.lastname@example.org