1) While connected to HDMI monitor, begin booting Cubox-i4 Pro with SD card flashed with 2.1.2 for Cubox i https://images.offensive-security.com/arm-images/kali-2.1.2-cubox-i.img.xz
2) Connect to Cubox-i4 Pro via USB Serial: screen /dev/tty.usbserial-DB00ECM0 115200
3) Watch it boot and notice that your monitor flashed some text for a while then went blank
4) Observe this text on serial connection:
[ OK ] Stopped Light Display Manager.
Starting Light Display Manager...
[ OK ] Started Light Display Manager.
[ OK ] Stopped Light Display Manager.
Starting Light Display Manager...
[ OK ] Started Light Display Manager.
[ OK ] Stopped Light Display Manager.
Starting Light Display Manager...
[ OK ] Started Light Display Manager.
[ OK ] Stopped Light Display Manager.
Starting Light Display Manager...
[ OK ] Started Light Display Manager.
[ OK ] Stopped Light Display Manager.
[FAILED] Failed to start Light Display Manager.
See 'systemctl status lightdm.service' for details.
5) Follow the instructions to get details:

systemctl status lightdm.service

lightdm.service - Light Display Manager
   Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; vendor preset: 
   Active: inactive (dead) (Result: exit-code) since Mon 2016-09-26 21:26:00 UTC
     Docs: man:lightdm(1)
  Process: 347 ExecStart=/usr/sbin/lightdm (code=exited, status=1/FAILURE)
  Process: 343 ExecStartPre=/bin/sh -c [ "$ (cat /etc/X11/default-display-manager
 Main PID: 347 (code=exited, status=1/FAILURE)

Sep 26 21:25:59 kali systemd[1]: lightdm.service: Unit entered failed state.
Sep 26 21:25:59 kali systemd[1]: lightdm.service: Failed with result 'exit-code'
Sep 26 21:26:00 kali systemd[1]: lightdm.service: Service hold-off time over, sc
Sep 26 21:26:00 kali systemd[1]: Stopped Light Display Manager.
Sep 26 21:26:00 kali systemd[1]: lightdm.service: Start request repeated too qui
Sep 26 21:26:00 kali systemd[1]: Failed to start Light Display Manager.

6) Also try "startx" and observe additional error info
Current version of pixman: 0.33.6
Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Thu Feb 11 16:43:28 2016
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
(EE)
Fatal server error:
(EE) no screens found(EE)
(EE)
Please consult the The X.Org Foundation support
at http://wiki.x.org
for help.
(EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
(EE)
(EE) Server terminated with error (1). Closing log file.
xinit: giving up
xinit: unable to connect to X server: Connection refused
xinit: server error

Due to the age of the OS (Kali Moto [v1], Kali Safi [v2], Kali Rolling 2016.x), these legacy versions are no longer supported.
We will be closing this ticket due to inactivity.

Please could you see if you are able to replicate this issue with the latest version of Kali Linux - https://www.kali.org/downloads/)?

If you are still facing the same problem, feel free to re-open the ticket. If you choose to do this, could you provide more information to the issue you are facing,and also give information about your setup?
For more information, please read: https://kali.training/topic/filing-a-good-bug-report/