@betaman@Elmojo, I know this is an 18 page thread right now, but I really, really recommend reading it all. Keep in mind the first few pages are teething issues with older versions of the software and getting it running in Unraid at all, so maybe just skim those, but really, I think reading through the whole thread will help to get some context on how things work.
I currently have 10 different machines actively backing up to one of my instances, and over the years have done many file level retrievals both directly from the server UI and the client app. I've also done a couple bare metal restores to brand new drives that went flawlessly, all this over WAN, as the Unraid server hosting my UrBackup instance is 10 miles or more from all but 2 of the machines or VM's it's protecting.
You can also set up UrBackup users with privileges to only manage the machines you assign to them, so when they log in to the UI they only see their backups.
This really can be business level backups, I've totally replaced carbonite for several people and saved them a bunch of money, since UrBackup happily manages Microsoft Server products, where any of the cloud services charge big $$$ for their server tiers. The people I do this for know up front what building their data is in, and how it's protected, instead of trusting a faceless corp.