Hi,
Azure File Sync is fully supported on DFS Namespace servers, you can install the Azure File Sync agent on one or more DFS Namespace member servers to sync data between the server endpoints and the cloud endpoint.
For more information, see:
Planning for an Azure File Sync deployment
https://learn.microsoft.com/en-us/azure/storage/files/storage-sync-files-planning#distributed-file-system-dfs
Interoperability with Azure virtual machines
https://learn.microsoft.com/en-gb/windows-server/storage/dfs-namespaces/dfs-overview#interoperability-with-azure-virtual-machines
Best regards,
Leon