Hi,
Hope everything goes well.
If you are both co-management enabled and the tenant attach process completed in your SCCM environment, co-managed devices may be duplicated in the Microsoft Endpoint Manager admin center. We can uncheck the Upload to Microsoft Endpoint Manager admin center option in the Configure upload tab to have a try. Refer to:
https://learn.microsoft.com/en-us/mem/configmgr/tenant-attach/device-sync-actions
Best regards,
Simon
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