Ubuntu 17.10 (Xorg), gnome shell 3.26.2, kernel 4.13.0-43-generic.
I have three monitors attached to my computer. Everything worked great, but a couple days ago I noticed that when booting my computer - with all three monitors turned on - the Ubuntu splash screen appears on only one of the monitors - the other two remain black. When the boot process gets to the login screen, then all three monitors begin working correctly, and everything is fine from that point on.
The monitors are:
The boot splash screen appears only on #1 (VGA-1).
Why is the Ubuntu splash screen appearing on only one of the monitors?
How do I control which monitors the splash screen appears on?
This may sound like a minor problem, but it isn't really: There are several users who use this computer, most of them very computer illiterate. For them they do not need to use all three monitors. So, to keep things simple for them I have set the nicest monitor in the middle (#2, HDMI-2), and have told them they only need to turn on that monitor. The problem is that if they turn on only that monitor and start the computer, during the minute or so of boot time they see nothing, only a black screen, (because the splash screen does not appear on that monitor), so without that visual feedback they don't know if the computer is starting properly or not.