mjhjmtu

I have a MacBook Air (13-inch, Early 2015) and I run Ubuntu 16.04 on it. Under Ubuntu I cannot detect the external monitor with the thunderbolt cable. Settings -> Displays doesn't show any other available display.

However the external display gets recognized under Ubuntu only if I reboot from my MacOSX session with the said display already plugged. If I unplug and replug it, the display is not recognized anymore.

Any solution on how to correctly set up the external display directly from Ubuntu (or any linux)?

EDIT 1

I plugged the monitor from MacOSX (El Capitan). I rebooted on Ubuntu. I open the Displays interface:

Both my built-in monitor and the external are correctly recognized. I used xrandr if it can provide more information:

$ xrandr
Screen 0: minimum 8 x 8, current 2560 x 2340, maximum 32767 x 32767
eDP1 connected primary 1440x900+0+1440 (normal left inverted right x axis y axis) 286mm x 179mm
 1440x900 59.84*+ 59.89 
 1360x768 59.80 59.96 
 1280x800 60.00 
 1152x864 60.00 
 1024x768 60.00 
 800x600 60.32 56.25 
 720x450 60.00 
 640x480 59.94 
DP1 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
 2560x1440 59.95*+
 1280x720 59.86 
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Then I unplugged the external monitor, and plugged it again. My Displays:

And the output from xrandr:

$ xrandr
Screen 0: minimum 8 x 8, current 1440 x 900, maximum 32767 x 32767
eDP1 connected primary 1440x900+0+0 (normal left inverted right x axis y axis) 286mm x 179mm
 1440x900 59.84*+ 59.89 
 1360x768 59.80 59.96 
 1280x800 60.00 
 1152x864 60.00 
 1024x768 60.00 
 800x600 60.32 56.25 
 720x450 60.00 
 640x480 59.94 
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

EDIT 2

I noticed that in order for the monitor to be recognized with Ubuntu, I only need to (re)boot with the thunderbolt plug attached. It doesn't have to be rebooted from the MacOS. But I still haven't found how to solve the issue.