Ubunutu GUI not showing after installation with sudo apt-get install gdm3 ubuntu-unity-desktop

Please provide the following info (check/uncheck the boxes after creating this topic):
Software Version
DRIVE OS Linux 5.2.6
DRIVE OS Linux 5.2.6 and DriveWorks 4.0
DRIVE OS Linux 5.2.0
DRIVE OS Linux 5.2.0 and DriveWorks 3.5
NVIDIA DRIVE™ Software 10.0 (Linux)
NVIDIA DRIVE™ Software 9.0 (Linux)
other DRIVE OS version

Target Operating System

Hardware Platform
NVIDIA DRIVE™ AGX Xavier DevKit (E3550)
NVIDIA DRIVE™ AGX Pegasus DevKit (E3550)

SDK Manager Version

Host Machine Version
native Ubuntu 18.04


I was able to install the GUI for the target with the instructions from the two posts here:
Install DRIVE with SDK Manager :: DRIVE Platform Installation Guide with NVIDIA SDK Manager
NVIDIA DRIVE OS 5.2 Linux SDK Developer Guide : System Software Components and Interfaces | NVIDIA Docs (the section Installing GUI on the Target)

From the second link above, the steps 1 to 5 worked and everything went through.

However, after rebooting and connecting the Pegasus to an external monitor, I still do not see the GUI. What is the reason for this?

Thanks in advance!

Dear @kn10,
Please check if below topics helps?