Comment # 10 on bug 1036342 from Mark Draheim

(In reply to Markos Chandras from comment #9)
> Not sure
> if it helps or not, but plasma5 works fine with that package installed so
> this feels like a gnome issue to me :/

and I almost thought that your problem is essentially the same as in

https://bugzilla.opensuse.org/show_bug.cgi?id=1017478

ie nouveau 1.0.14-2.1 and X dumping core early.

In your initial report you said that gdm loops. How then did you get a plasma5
session up?

The reason I ask is that the bug I referenced points a finger at sddm/QT/Plasma
but if you see the same problem with Gnome/GTK, then we can narrow it down to
Xorg/nouveau. Which I think is highly likely given that similar reports from
nouveau users pop up in the forums almost daily now.