New Ubuntu Latitude 5450 came with a restricted, sandboxed desktop

Hi, I'm hoping you can help me.

I recently got a Dell Latitude 5450 for work with Ubuntu installed.  (I have a personal Dell XPS with Ubuntu, so I'm familiar with the OS.)

When I unboxed the machine and powered it on, at first it seemed to bring me in as 'guest'.  On other Ubuntu laptops in the past, when I've powered on for the first time, it's walked me through the process of setting up my initial account, but that didn't happen here.

The 'guest' account loads into what seems to be a sandboxed environment.  I can set up Wi-Fi and get to Firefox or Chrome, but the only other applications available are Zoom and a file explorer I don't recognize.  

I can't get to a Linux terminal either with Ctrl-Alt-T or by searching for 'Terminal' in the software menu.  (I can't find anything in the software menu.)

I was able to get a terminal with root access only by booting from a live USB environment.  I had tried to use GRUB to get to a root window, but it seems that every option on the GRUB menu requires a username / password - which I don't have.

Anyway, from the terminal I created a new account called 'jason' and gave that account sudo privileges.

Unfortunately when I log in as 'jason', I'm still in that very restricted sandbox desktop environment.

It's like this machine was set up for a different purpose before I got it.  Does that make sense?

How do I unlock the proper full Ubuntu experience on my Latitude 5450?

I could try a workaround and install a fresh Ubuntu partition, but if GRUB is password-protected, I'm not sure I'd be able to boot into it.  Is there a default username/password I'm supposed to use for GRUB?

If I can provide any more information that would be helpful, please let me know.

Thanks very much,
Jason