Hi @Steve , welcome to Q&A forum!
There is currently no official migration tool that can migrate from SP2016 to SP2019. Usually the migration method we use is database migration.
Upgrade Procedure:
- Creating a new SharePoint Server 2019 farm
- Copying SharePoint Server 2016 databases to the new environment
- Upgrading databases and service applications from SharePoint 2016
- Upgrading SharePoint Server 2016 site collections
Please refer to this official article for more information:
Upgrade databases from SharePoint 2016 to SharePoint Server 2019
And here is a blog about content database migration from SP2016 to SP2019:
Migrate SharePoint 2016 To SharePoint 2019 Environment Using Content Database Migration
Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.
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