Gianni,
We use RUM but pull down updates directly from Adobe. Lightroom is one of the apps that the update manager doesn't touch (like Acrobat, CC Desktop App and, I believe, Muse). Our lab systems are all built with installers created by the CC Packager tool and are anonymous (licensed with the serialization tool and deployed without the Desktop App). When a new Lightroom release comes out, I found I have to build a new install package. On the Mac OS this works fine. For Windows, I found I have to re-serialize the system after installing the updated Lightroom. So I built that step into the install batch script I use.
Hope this helps. I spent the better part of an afternoon figuring this out the first time I had to deal with it.