Hi,
This plugin is still available. It is included by default with HikaSerial. Its role is to generate serial numbers with the EAN format.
If you want to display an EAN code on the product page, make it searchable, and exportable in CSV, you can just create a custom field of the table "product" and of the type "text" via the menu Display>Custom fields.
That way, in each product edit form, you'll be able to enter the EAN code in that custom field. And you have display settings in the custom field to make it display on the product page on the frontend.
And you can also edit the text filter you already have to search on your products name via the menu Display>Filters and select that custom product field in there so that when you enter an EAN code in the filter input, it will search on that custom field too.
And for the Joomla search module, you can edit the HikaShop product search plugin via the Joomla plugins manager and select that custom field column name to be able to use it for searches.
And regarding the CSV export, both the "export" button of the products listing in the backend, and the mass action product export action will have that custom field column in them automatically.