How do I manage Azure AD and local active directory domain users and devices?

Looks like a DNS issue. If the devices are ADDS joined they may be pointing to local DNS servers without appropriate DNS forwarding. Ensure records such as enrollment.manage.microsoft.com can be resolved.

If you’re not using automatic enrollment as part of your enrollment or provisioning solution, we recommend creating a domain name server (DNS) alias, called a CNAME record type, for your MDM servers. Instructions can be found at Enable auto-discovery of Intune enrollment server.

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