Thank you for your post and I apologize for the delayed response!
When it comes to using Managed Identities from a Container Instance, are you able to share any documentation that you followed to enabled this? This way I can gain a better understanding of our issue. I've also reached out to our AKS team regarding this so they can take a look into this issue as well.
How to use managed identities with Azure Container Instances
Is there support for Azure Kubernetes Containers?
Updating to version 3 throws "No managed identity endpoint found" with managed identity
AKS 1.15.11 getting : ManagedIdentityCredential authentication unavailable, no managed identity endpoint found when using eventhub
Azure Container Instance - Managed Identity not available when container first deployed or restarted
If you have any other questions or would like to work with our support team to get this issue resolved, please let me know.
Thank you for your time and patience!