Connor Jackson

Yes, see: https://github.com/benahm/TestDataFactory/blob/master/docs/EXAMPLES.md, you can create records whilst setting Boolean doInsert to false, this give you a list of records that you can upsert using the external ID like you...

@sarahbrock this Salesforce Known issue is likely the cause of your failed install. https://trailblazer.salesforce.com/issues_view?id=a1p3A000001PYZAQA4. You could clone the repo, and then change the layout as per the Known Issue work...