Would you by any chance remember what version of Python did you install?
Also, what is your VM like? Mine is a VMWare Ubuntu 18.04 Guest running over Windows 10 and it gets stuck in step 3. It is like it doesn’t see my Xavier even though VMWare reports it is connected.
As far as I know it is hard to get SDK Manager work with VM due the reconnections that are done during the flashing process, here is a post for reference: