I am having a hard time finding out who else has run into this issue, but when I try to run the migration for the data, I am getting this error:
[2020-08-21 18:59:11][ERROR]: Not mapped id key 23 found for eav_entity_attribute.attribute_set_id
I have never seen this before. I know what it's looking for, but it doesn't make sense. There was never an attribute id of 23. And I even went ahead on the older Magento and added in a test Product Attribute Set which then listed the ID as 23. So you would think now that it's created, it would find it, but I'm still getting the same error.
When we are migrating the data, we gone through this issue, this is because the attribute id re-create and during the migration, as you have 23 id in your data, but for further process, its not find to relocate it. Just you have to do the Proper-mapping before running the migration data, it cant appear again.