Im having a similar problem. I have a ThinkPad T520, running xfce 4.12 on ubuntu 18.04.
I have tried this command with and without '--auto': 'xrandr --output LVDS-1 --auto --same-as DP-1-1' Here is my xrandr output: Screen 0: minimum 320 x 200, current 1600 x 900, maximum 8192 x 8192 LVDS-1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 345mm x 194mm 1600x900 59.99*+ 59.99 59.94 59.95 59.82 50.00 1440x900 59.89 1400x900 59.96 59.88 1440x810 60.00 59.97 1368x768 59.88 59.85 1360x768 59.80 59.96 1280x800 59.99 59.97 59.81 59.91 1152x864 60.00 1280x720 60.00 59.99 59.86 59.74 1024x768 60.04 60.00 960x720 60.00 928x696 60.05 896x672 60.01 1024x576 59.95 59.96 59.90 59.82 960x600 59.93 60.00 960x540 59.96 59.99 59.63 59.82 800x600 60.00 60.32 56.25 840x525 60.01 59.88 864x486 59.92 59.57 800x512 60.17 700x525 59.98 800x450 59.95 59.82 640x512 60.02 720x450 59.89 700x450 59.96 59.88 640x480 60.00 59.94 720x405 59.51 58.99 684x384 59.88 59.85 680x384 59.80 59.96 640x400 59.88 59.98 576x432 60.06 640x360 59.86 59.83 59.84 59.32 512x384 60.00 512x288 60.00 59.92 480x270 59.63 59.82 400x300 60.32 56.34 432x243 59.92 59.57 320x240 60.05 360x202 59.51 59.13 320x180 59.84 59.32 VGA-1 disconnected (normal left inverted right x axis y axis) LVDS-1-2 disconnected (normal left inverted right x axis y axis) VGA-1-2 disconnected (normal left inverted right x axis y axis) DP-1-1 connected (normal left inverted right x axis y axis) 1920x1080 60.00 + 50.00 59.94 1920x1080i 60.00 50.00 59.94 1680x1050 59.88 1600x900 60.00 1280x1024 75.02 60.02 1280x800 59.91 1152x864 75.00 1280x720 60.00 50.00 59.94 1024x768 75.03 60.00 832x624 74.55 800x600 75.00 60.32 720x576 50.00 720x480 60.00 59.94 640x480 75.00 60.00 59.94 720x400 70.08 DP-1-2 disconnected (normal left inverted right x axis y axis) DP-1-3 disconnected (normal left inverted right x axis y axis) 1280x800 (0x51) 71.000MHz +HSync -VSync h: width 1280 start 1328 end 1360 total 1440 skew 0 clock 49.31KHz v: height 800 start 803 end 809 total 823 clock 59.91Hz 1024x768 (0x57) 65.000MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz v: height 768 start 771 end 777 total 806 clock 60.00Hz 800x600 (0x5a) 40.000MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz v: height 600 start 601 end 605 total 628 clock 60.32Hz 640x480 (0x60) 25.175MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.47KHz v: height 480 start 490 end 492 total 525 clock 59.94Hz -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg-server in Ubuntu. https://bugs.launchpad.net/bugs/1771185 Title: Secondary monitor not connecting in 18.04 LTS To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1771185/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp