@Vij, Thanks for posting in Q&A. For the devices which shows ConfigMGR, it means the device still managed by configuration manager. It will affect when old configuration manager is removed. For co-managed device, we can follow the steps in "Option 3 - Move from Configuration Manager to Intune" to make the devices can still be managed when the old Configuration Manager is removed.
For the registry key, it determines which service is responsible for managing specific workloads on the device. value 1 means Intune is the MDM provider. You can switch the workload via the steps in the above link and see if it is changed.
Please try the above suggestion and if there's any update, feel free to let us know.
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