@Martin Camm Welcome to Microsoft Q&A, Thank you for posting your query here!
Azure File Sync works on Direct Attached Storage (DAS) locations and does not support sync to Network Attached Storage (NAS) locations. This fact makes a migration of your files necessary and this article guides you through the planning and execution of such a migration.
Migrate from Network Attached Storage (NAS) to a hybrid cloud deployment with Azure File Sync
A user of Active Directory, which is their on-premises domain controller, can natively access an Azure file share. So can a user of Azure Active Directory Domain Services (Azure AD DS). Each uses their current identity to get access based on share permissions and on file and folder ACLs. This behavior is similar to a user connecting to an on-premises file share.
The alternative data stream is the primary aspect of file fidelity that currently can't be stored on a file in an Azure file share. It's preserved on-premises when Azure File Sync is used.
Learn more about Azure AD authentication and Azure AD DS authentication for Azure file shares.
Additional information: Currently, Azure File Sync supports only Windows Server 2019, Windows Server 2016, and Windows Server 2012 R2. At this time, we don't have any other plans we can share, but we're open to supporting additional platforms based on customer demand. Let us know at Azure Files UserVoice what platforms you would like us to support.
If port 445 is blocked or some restriction, you may setup the VPN for the storage account. Learn more here
Hope this helps!
Kindly let us know if the above helps or you need further assistance on this issue.
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