There are quite a few different active directory or ldap servers out there. They can provide user access and authentication to omv. There are many threads going back to the early days of omv. There is even a plugin.
The biggest issue in most threads is some setting needs to be tweaked. Debian now has two packages that can now detect many settings, sssd and realmd. Maybe others too? This should solve many of those issues. If someone updated the plugin or rewrote that would be awesome.
For reference here are a few threads that may be helpful. No particular order. If you know of others I will add them here.