If you proceed without blocking updates externally, you should get to the home screen as fast as possible and immediately block updates internally. Note that as Amazon releases new software versions, this guide may no longer work.
It is impossible to continuously test if this guide still works because I can’t possibly afford to buy a new Fire TV or Fire TV Stick every time Amazon updates the software version that their devices leave the factor with.
Note that it is possible to load the wrong firmware on a device in the event that the software packages are somehow mixed up between these various products.
Do users of your Delphi application actually see the progress bar moving?