How to change Content Type Hub URL in Managed Metadata Service?
In SharePoint 2019 or SharePoint 2016, to change Content Type Hub URL in Managed Metadata Service, you should use the below PowerShell cmdlet:
Set-SPMetadataServiceApplication -Identity "Managed Metadata Service Name" -HubURI "Site COllection URL"
Note: In SharePoint Central Administration, Once you set the Content Type Hub URL in Managed Metadata Service, you CAN'T change it again from central administration.
For more details, Please check SharePoint 2019 Configure Content Type Hub