Why do you mention “fbset”, will it be any difference if you use xrandr to change mode?
Because xrandr cannot execute from tty/ssh console.
# export DISPLAY=:0
# xrandr
No protocol specified
Can't open display :0
Executing from GUI,
It seems no difference with fbset.
$ xrandr
Screen 0: minimum 8 x 8, current 5120 x 1440, maximum 32767 x 32767
HDMI-0 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 600mm x 340mm
2560x1440 59.96*+
2560x1080 60.01 59.95 50.00 30.00 29.97 25.00 24.00 23.98
2048x1152 60.01
1920x1440 60.01
1920x1200 59.89
1920x1080 60.00 59.95 50.00 30.00 29.97 25.00 24.00 23.98
1680x1050 59.96
1440x900 59.89
1440x576 50.00
1440x480 59.94
1280x1024 75.03 60.00
1280x720 60.00 59.94 50.00
1152x864 75.00
1024x768 75.03 70.07 60.01
832x624 75.05
800x600 75.00 72.19 60.32 56.25
720x576 50.00
720x480 59.94
720x400 70.04
640x480 75.00 72.81 67.06 59.94 59.94
DP-0 connected 2560x1440+2560+0 (normal left inverted right x axis y axis) 600mm x 340mm
2560x1440 59.96*+
2560x1080 60.01 59.95 50.00 30.00 29.97 25.00 24.00 23.98
2048x1152 60.01
1920x1440 60.01
1920x1200 59.89
1920x1080 60.00 59.95 50.00 30.00 29.97 25.00 24.00 23.98
1680x1050 59.96
1440x900 59.89
1440x576 50.00
1440x480 59.94
1280x1024 75.03 60.00
1280x720 60.00 59.94 50.00
1152x864 75.00
1024x768 75.03 70.07 60.01
832x624 75.05
800x600 75.00 72.19 60.32 56.25
720x576 50.00
720x480 59.94
720x400 70.04
640x480 75.00 72.81 67.06 59.94 59.94
Will you see such issue if it is single DP or single HDMI case?
No, the red noise happens only play HDMI and DP simurately.
Will you see such issue if you use other display modes?
I changed display modes from Ubuntu GUI[All Settings/Displays].
Desktop environment was enable.
1920x1080 could see same red noise like 2560x1440.
1280x720 was no problem.