currently working on this exact problem on 3.80. I wrote a C# app to create a CSV file from a photo image list. Each photo image is used to create six separate product SKUs. I use LibreOffice (excel clone) to create a xlsx file from the csv. The import works perfectly from nopCommerce standpoint EXCEPT everything I import is Not Individually Visible, Not Published, and the Backorders field stays at its default value of No Backorders. The photos are fine, the search engine names, prices, etc are good. Still trying to track down why I can't get the fields set properly even though the spreadsheet shows then set.  Of note, I used an export from 3.80 as a template for the headers and field values.

When I make a breakthrough. I will certainly pass on the details.