Hello James Cook,
Welcome to the MS Q&A forum.
Yes, correct, the following Virtual Machine features are currently not supported with Trusted Launch:
- Azure Site Recovery
- Azure Automanage
- Ultra disk
- Managed Image (Customers are encouraged to use Azure Compute Gallery)
- Nested Virtualization (most v5 VM size families supported)
You are not the first user who asked about this limitation. I found the similar feature requests: Azure Site Recovery support for Trusted Launch VM, Need option to Disable Trusted Launch for Running VM, Azure Site Recovery NA replication of VMs with UEFI and SecureBoot enabled on the feedback forum. If interested, you may upvote it.
In general, Azure feature or product team would check feasibility of a feature request, prioritize against existing feature backlog, add them in roadmap as appropriate and would announce and/or update the related Azure document once a feature request is addressed.
Sincerely,
Olga Os.