@nfli this could be an issue with your /etc/apt/sources.list, documented (and still unresolved) in this thread: Empty /etc/apt/sources.list on clean DRIVE OS 126.96.36.199 image
^ Some installs of the DRIVE software result in an empty apt sources file which keeps apt from finding any packages, even if your Xavier A has an internet connection.
Could you run
cat /etc/apt/sources.list from your AGX Xavier A and post the results here? If that command doesn’t return anything, it means your sources.list file is empty, and you should fill it with the contents laid out in the thread linked above, then run
sudo apt update and try installing packages again.
You don’t need to compile ROS from source on the AGX – you can install it with apt, as long as you have internet and a valid sources.list file.