Two more trials without any improvement:
Using kernel-4.9.0-0.rc2.git0.2.fc26 does not help. I had no reason to
think it would, but now that ssh to my RPi3 works well, it was easy to
Changing the display to a Dell P2415Q (3840x2160 resolution, HDMI
input) does not help. Again, no reason to think it would, but the
world has a lot of quirky hardware and this helps me believe it is not
a display device issue.
The last line I see before the display goes blank is:
fb: switching to vc4drmfb from simple
which is no surprise.
Journal and dmesg files are at: http://ryniker.org/Fedora/arm/