Hi @Nad Mal ,
if you already running an AADDS you don't need a global admin of the Azure AD to join a VM to the AADDS domain.
Instead you need to use a user that is member of the AAD DC Administrators
group (in Azure AD). This user doesn't require Global Admin membership in Azure AD.
https://learn.microsoft.com/en-us/azure/active-directory-domain-services/tutorial-create-instance-advanced
Also verify the domain name of the AADDS is used to join the VM (not the domain name of the Azure AD).
Last but not least: Make sure the Virtual Network of the WVD hosts is peered with the vNet of the AADDS and DNS is configured properly. The AADDS domain name should be resolved and reached if you ping the domain name from a VM in the WVD host vNet.
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Regards
Andreas Baumgarten