I would like to know about SharePoint 2016 upgrade to 2019 on-premise.
Does SharePoint support in-place upgrade?
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In-place upgrade is not supported. Review the documentation Upgrade to SharePoint Server 2019 for information on how to perform a 2016 to 2019 upgrade using the database attach method.
No, you can't do the in place upgrade.only supported way is database upgrade or using 3rd party tools.
You can review this article "Overview of the upgrade process to SharePoint Server 2019" for more information