Comment # 1 on bug 1127979 from Stefan Dirsch

I believe you have some strange limits configured for the monitor in your
/etc/X11/xorg.conf. I suggest to remove this file completely and try again.

Apart from this Dell Precision 5520 is an Optimus system (Intel
Kabylake/NVIDIA). Should work with NVIDIA GPU as rendering device with the help
of suse-prime package now. We have it running here with sle15-sp1 Beta4 on this
machine.