I've been struggling to get a third screen working which stopped after changing the monitor (previously this did work on USB displayLink). I had EDID errors on startup so now have generated my own xorg.conf file as below. The screen now starts, but shows a ubuntu loading screen stating 'Started Light Display Manager' but isn't recognised in the screen settings.
Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BusID "PCI:1:0:0"
EndSection
Section "Device"
Identifier "DisplayLinkDevice"
driver "displaylink"
Option "fbdev" "/dev/fb1"
Option "UseEDID" "False"
EndSection
Section "Monitor"
Identifier "Monitor0"
ModelName "S24D590"
VendorName "SAM"
# Monitor Manufactured week 23 of 2015
# EDID version 1.3
# Analog Display
Option "SyncOnGreen" "true"
DisplaySize 520 290
Gamma 2.20
Option "DPMS" "true"
Horizsync 30-81
VertRefresh 56-75
# Maximum pixel clock is 170MHz
#Not giving standard mode: 1152x864, 75Hz
#Not giving standard mode: 1280x720, 60Hz
#Not giving standard mode: 1280x800, 60Hz
#Not giving standard mode: 1280x1024, 60Hz
#Not giving standard mode: 1440x900, 60Hz
#Not giving standard mode: 1600x900, 60Hz
#Not giving standard mode: 1680x1050, 60Hz
Modeline "Mode 0" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
EndSection
Section "Monitor"
Identifier "Monitor1"
ModelName "S24D590"
VendorName "SAM"
# Monitor Manufactured week 23 of 2015
# EDID version 1.3
# Analog Display
Option "SyncOnGreen" "true"
DisplaySize 520 290
Gamma 2.20
Option "DPMS" "true"
Horizsync 30-81
VertRefresh 56-75
# Maximum pixel clock is 170MHz
#Not giving standard mode: 1152x864, 75Hz
#Not giving standard mode: 1280x720, 60Hz
#Not giving standard mode: 1280x800, 60Hz
#Not giving standard mode: 1280x1024, 60Hz
#Not giving standard mode: 1440x900, 60Hz
#Not giving standard mode: 1600x900, 60Hz
#Not giving standard mode: 1680x1050, 60Hz
Modeline "Mode 0" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
EndSection
Section "Monitor"
Identifier "DisplayLinkMonitor"
ModelName "S24D590"
VendorName "SAM"
# Monitor Manufactured week 23 of 2015
# EDID version 1.3
# Analog Display
Option "SyncOnGreen" "true"
DisplaySize 520 290
Gamma 2.20
Option "DPMS" "true"
Horizsync 30-81
VertRefresh 56-75
# Maximum pixel clock is 170MHz
#Not giving standard mode: 1152x864, 75Hz
#Not giving standard mode: 1280x720, 60Hz
#Not giving standard mode: 1280x800, 60Hz
#Not giving standard mode: 1280x1024, 60Hz
#Not giving standard mode: 1440x900, 60Hz
#Not giving standard mode: 1600x900, 60Hz
#Not giving standard mode: 1680x1050, 60Hz
Modeline "Mode 0" 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync
EndSection
#Section "Monitor"
# Identifier "DisplayLinkMonitor"
#EndSection
Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen1"
Device "Device0"
Monitor "Monitor1"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1920x1080"
EndSubSection
EndSection
Section "Screen"
Identifier "DisplayLinkScreen"
Device "DisplayLinkDevice"
Monitor "DisplayLinkMonitor"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1920x1080"
EndSubSection
EndSection