Using Exchange Custom Attributes for Groups Through the Microsoft Graph
Microsoft has released limited Graph support for accessing Exchange custom attributes in groups synchronized from on-premises environments. Not every type of Entra group is available on-premises, so we’re really talking about distribution groups and security groups. In any case, real-only access to the fifteen custom attributes is available via Graph API and the Get-MgGroup cmdlet. Now it’s up to you to do something inventive with the information.