The new Lightroom CC removed the ability to display images on a secondary display. That's a horrific loss of functionality. What sounded like a promising update turned into a step backwards. Come on, Adobe, get your act together!
It's a 1.0 release of a new app, completely separate from an upgrade of Lightroom. You can see some of the other features that haven't made it into CC yet here: Lightroom CC vs. Lightroom Classic – Which Do I Need?
The name of the program is Lightroom CC, the exact same as before. It's Adobe's premier photo organizing and editing app. It may be a completely separate & new app from before, but if Adobe is going to call it the same thing, I expect it to at least have the functionality of its prior namesake. The inability to display a single image on a secondary display is a tremendous loss of functionality that destroys my workflow. That's a downgrade, not an upgrade. Adobe gets an F on this one.