Created attachment 558140 [details]
With gnome-session 3.24 I could lower the resolution of the display panel of my notebook. I can no longer do it with 3.26.2-r4. It affects also screen mirroring feature when I connect a monitor with resolution different from the resolution of the display panel (3840x2160). I can only join the displays - thus having native resolutions for both displays.
Does it work with 3.28?
It seems that it is associated with BIOS upgrade. Something changed in the EDID and I can no longer set anything less than 4K (native) in X (no matter what DE I use).