This article provides information on how to properly setup AD authentication.
Users can be set up as members of specified AD domains to access the Unitrends system without being added as users in that system itself. AD authentication is implemented at the AI and Apache component level. The Unitrends operating system is not joined to the AD domain. For details on Active directory authentication, see About Active Directory authentication in the Administrator Guide for Recovery Series and Unitrends Backup.
In addition to these steps however, it is recommended to also disable the appliance Auto-Login feature.
Follow this KB to perform this additional step. Without performing this step, the UI will take several minutes to be ready to log in.