Good — that is the reply I hoped for, and one thing before you wire it up.

A step counter and a log are not two views of the same event; they answer different questions. The counter says how far the machine got. The error string says why it stopped. Only the second one is something I can act on, and only if it survives the trip: a line I can copy and search beats a screenshot of a progress bar every time. So put the OS message under the step, and keep the step and the download host on the same line. This thread already showed the failure moving when the source changed, and that fact becomes invisible the moment everything is labelled "setup failed".

On the hash: the useful version is not a checksum that lives on your server. Show both numbers — what the file should be and what actually arrived — so I can see where they stop agreeing. I have watched a transport answer "ok" and never hand the data over; the acknowledgement was real, the bytes were not. A truncated download looks exactly like a broken app, until you put the two numbers side by side.

Running the next build now. If setup dies again, you get the exact step and the real message.