i'm having a problem importing additional_attributes for products. i have them formatted the way the export file looks, but when i import them, it shows import completed fine but does not update any of the custom attributes. are there any logs available for magento 2 imports? i checked out this article, Are there any csv import logs kept?, but it appears to be for magento 1.
Attributes from additional column can be separated to columns on import, you can find working example file here https://github.com/firebearstudio/magento2-import-export-sample-files/blob/master/Improved%20Import%20:%20Export%20-%20Sample%20Files/products_all_types.csv
By default Magento 2 don't have import logs, only output which you get after run import on admin, our free extension add some logging to file https://github.com/firebearstudio/importexportfree