After more testing, I'm hitting the same problem on a clean of the server on Ubuntu 16.04.2. No clients, no other settings changed from their defaults. Just LDAP.
Also, when I enable LDAP for the first time and use the following query...
...the website hangs when trying to save the settings. It appears to save the settings because I am prompted to log in with AD credentials. But that just hangs after submitting, too. At this point, I need to revert the snapshot on the VM in order to use the UrBackup web interface again.
AD login only works at all if I narrow the search, like so...
But again, still can't access the Backups page.
I understand LDAP/AD authentication is experimental, but I'd like to help troubleshoot these problems with you however I can.