Hi @Marcus Wong Theen Nam ,
SPMT supports migration to SharePoint, OneDrive, and Teams from SharePoint Server 2010, 2013, and 2016.
Reference: https://learn.microsoft.com/en-us/sharepointmigration/introducing-the-sharepoint-migration-tool
Migration Manager helps you migrate your on-premises file share content to sharepoint online.
Reference: https://learn.microsoft.com/en-us/sharepointmigration/mm-get-started
So you can not migrate your local file shares (NAS) to SharePoint 2019 server (On-Premise) using SPMT or Migration Manager. There is currently no official tool to do this.
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