Hello Adam
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
Nested virtualization in Azure Stack Hub is supported from from release 2102 and later.
Please check this document that has he details: https://learn.microsoft.com/en-us/azure-stack/user/azure-stack-vm-considerations?view=azs-2206&tabs=az1%2Caz2#vm-differences
Hope this helps.
If you need further help on this, tag me in a comment.
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