Ubuntu – Multiple users on one computer with different monitors on Ubuntu/Linux

This is a script I made on Linux Mint with XFCE for the same kind of setup. Not using Xinerama. My setup was 1st monitor portrait, 2nd and 3rd, landscape. Worked like a charm. The 5 second pause at start was because it was set to start with session, and if it was run too early, it was not working correctly.

Note also that in my specific example, I had to align screens on bottom as one was higher than the others. Aligning on top was not giving the expected behavior.

In the end, using xrandr was the only way I got it work the way I wanted.

Give it a try with your own settings

#!/bin/bash
sleep 5
xrandr --size 5040x1920 --output HDMI-0 --mode 1920x1080 --pos 1200x840 --primary \
--output DVI-1-1 --mode 1920x1080 --pos 3120x840 \
--output DVI-0 --mode 1920x1200 --pos 0x0 --rotate left

I made an article on my blog, however this is in french: https://akim.sissaoui.com/linux-attitude/un-bureau-etendu-sur-trois-ecrans-avec-deux-cartes-graphiques/

Even simpler test!

Just swap one of your monitors to the onboard VGA output and see if it's displaying!

No

What motherboard do you have?

According to Belarc=> Board: ASUSTeK Computer INC. V-M2NC61P 

A google search shows this is an 'V-Series M2NC61P Asus PC (Desktop Barebone)' and reading the manual shows (in the BIOS/Advanced/Southbridge Configuration)

*Primary Graphics Adaptor [PCIE -> PCI -> IGP]*
Allows you to set the display decives priority.
Configuration options: [PCIE -> PCI -> IGP] [IGP -> PCI -> PCIE]

Usually the motherboards which disable onboard video actually do it on a hardware level - you would not see a display adaptor listed in device manager, this would be your next port of call to see if the onboard Graphics Adaptor is enabled with either of the 2 BIOS settings, if it is then you might be able to use that setting (aslong as your 8400 works) to have 3 displays...

If it doesn't your next step would be a 2nd Graphics card as explained by josh3736 below, but just remember - your motherboard only has ONE PCI-e x16 port (and 2 'standard' PCI).