I basically can see the same messages when booting with no screen attached and than plug just one monitor in. The result is the same, so black screens or rather  monitoring just reporting it is switching to powersave mode but xrandre seems to be happy:

DP-4 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080     60.00*+  59.96    50.00    59.94    59.93  
   1920x1200     59.95  
   1600x1200     65.00    60.00  
   1680x1050     59.95    59.88  
   1400x1050     74.76    59.98  
   1600x900      59.95    59.82  
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1400x900      59.96    59.88  
   1280x960      60.00  
   1440x810      59.97  
   1368x768      59.88    59.85  
   1280x800      59.99    59.97    59.81    59.91  
   1152x864      75.00  
   1280x720      60.00    59.99    59.86    60.00    50.00    59.94    59.74  
   1024x768      75.05    60.04    75.03    70.07    60.00  
   960x720       75.00    60.00  
   928x696       75.00    60.05  
   896x672       75.05    60.01  
   1024x576      59.95    59.96    59.90    59.82  
   960x600       59.93    60.00  
   832x624       74.55  
   960x540       59.96    59.99    59.63    59.82  
   800x600       75.00    70.00    65.00    60.00    72.19    75.00    60.32    56.25  
   840x525       60.01    59.88  
   864x486       59.92    59.57  
   720x576       50.00  
   700x525       74.76    59.98  
   800x450       59.95    59.82  
   720x480       60.00    59.94  
   640x512       75.02    60.02  
   700x450       59.96    59.88  
   640x480       60.00    75.00    72.81    75.00    66.67    60.00    59.94  
   720x405       59.51    58.99  
   720x400       70.08  
   684x384       59.88    59.85  
   640x400       59.88    59.98  
   576x432       75.00  
   640x360       59.86    59.83    59.84    59.32  
   512x384       75.03    70.07    60.00  
   512x288       60.00    59.92  
   416x312       74.66  
   480x270       59.63    59.82  
   400x300       72.19    75.12    60.32    56.34  
   432x243       59.92    59.57  
   320x240       72.81    75.00    60.05  
   360x202       59.51    59.13  
   320x180       59.84    59.32

Hello Ben,

could you please provide me with information about this known issue and fill it in the Doc Text field? If this bug does not have to be documented, please write it in a comment.

If you need a reference for filling up the Doc Text field, use this:

--

Cause

What actions or circumstances cause the bug to present (if known). Note that if the cause is not known or is not fully diagnosed, current hypotheses or theories should be noted.

Consequence

What happens when the bug presents. 

Workaround

What actions, if any, reduce the bug’s effects or prevent it from presenting entirely.

Result

If the bug’s effect is only reduced, what consequences still follow; if the bug is prevented, what restrictions does the workaround impose. 

--

If you have any other questions, please contact me.

Best regards,
Adam Kvítek

Hi Tomas,

This bug is on the list of candidates to be documented for RHEL 7.6 Release Notes.

Please, could you provide initial info in CCWR structure (cause, consequence, workaround, result) to document this bug?

Thank you!

Marie

Well this is a consequence of Bug 1457161, due to missing signed firmware for this particular graphics it can operate only using just single monitor output. The workaround is installing/build nvidia binary driver.

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.