Thank you for posting this in Microsoft Q&A.
As I understand you want to know what will happen to the access post subscription migration after Classic Admins gets retired.
Yes, as you mentioned when you transfer a subscription to a different Microsoft Entra directory, some resources are not transferred to the target directory. For example, all role assignments and custom roles in Azure role-based access control (Azure RBAC) are permanently deleted from the source directory and are not transferred to the target directory.
Once the transfer is successful in the target directory, sign in as the user that accepted the transfer request. Only the user in the new account who accepted the transfer request will have access to manage the resources.
Even though role assignments are removed during the transfer, users in the original owner account might continue to have access to the subscription through other security methods, including:
- Access keys for services like Storage.
- Management certificates that grant the user administrator access to subscription resources.
- Remote Access credentials for services like Azure Virtual Machines.
Let me know if you have any further questions.
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