Hi @Matthew Bell ,
Are you selling these devices without operating systems? There isn't a way that I am aware of to check the status without installing Windows if you don't have access to the tenant where these devices were joined. (Otherwise you would be able to check in the Azure portal itself.)
The two supported ways to check the Azure AD join status on the device itself are:
1.) Run dsregcmd /status
in Windows Powershell:
2.) Check the "Access work or school" settings to see if the device is listed.
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