Yes, you did mention that: Instlegato: command not found
Yes, I had come to that conclusion.
The trouble is, as noted here, the upgrade instructions just look like a load of Linux magic spells & incantations to me (the linux noob).
That was why I got stuck when I first received the Dev Kit (before the USB stick), and why I’m using the USB stick now - to try to avoid getting bogged-down in the arcane Linux world of building & installing toolchains, etc.
Can I just download a new USB stick image 
In fact, I can’t seem to find the old USB stick image (in case I mess it up) - I thought it was going to be made available to download
Or instructions to “clone” the stick - as a backup