We recently became aware of a known issue as part of the hybrid MDM migration. Customers mentioned that the Apple DEP device records are remaining in the ConfigMgr console. Unfortunately, once the MDM authority is changed to Intune, admins cannot remove these devices from the ConfigMgr console.
There’s two workarounds:
  1. If you happen to run into this prior to changing your MDM authority, then kindly delete the DEP records from ConfigMgr.
  2. If you’ve already migrated, then you can run the SQL command below on the ConfigMgr database, which will remove the records:
    Delete from MDMCorpOwnedDevices where DeviceType=8 and DiscoverySources=4
Here's documentation in case you would like additional information: