Azure ADDS default OU distinguished name for domain joining – i been using Azure ADDS with azure virtual desktop for domain joining and authentication. Azure ADDS work little differently then on-premises ADDS specially when it comes to OU structure and default OU.
If you want to join Azure VM to azure ADDS then you have to make sure the Azure ADDS dns ip is updated on the VM vnet DNS setting. additionally you can use powershell/ARM to join the VM to domain during VM creation process or you can do it manually by login in to the VM in case VM is already exist.
If you want to use domain join ARM extension on VM or other commands then you can pass the any OU path but you have to make sure that the account you are using has permission on the OU. In Azure ADDS the default computer OU is “AADDC Computers” (OU=AADDC Computers,DC=powershelltalk,DC=com) instead of “computers”.
so in case you want to use default OU path for computer domain join then you can use – OU=AADDC Computers,DC=powershelltalk,DC=com (change domain name). or you can create new OU and assign correct permission to service account and then use correct OU DN.