Hi @Nate C ,
Azure AD Premium and Basic editions are available for customers in China using the worldwide instance of Azure AD. Azure AD Premium and Basic editions aren't currently supported in the Azure service operated by 21Vianet in China. https://learn.microsoft.com/en-us/azure/active-directory/fundamentals/keep-me-signed-in
Based on this it would be supported with the worldwide instance but not for 21Vianet. I also reached out to the product team to see if there are any exceptions for admin accounts using Azure services operated by 21Vianet, and will reply with their response.
Let me know if this helps at all.
Thanks,
Marilee