Hi @Anonymous , thank you for posting in Q&A forum.
If you mean to use User Profile Service as the source, SharePoint does not support user profile sync from SharePoint Server 2019 to Active Directory.
We can only use SharePoint Active Directory Import or External Identity Manager (Microsoft Identity Manager) for user profile sync in SharePoint Server 2019.
Please provide detailed information if we have misunderstood your requirement. Thank you for your understanding.
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