I think unman was right. It was super slow, but as TheGardner said, it was variable.
I started over and it was moving at around half a meg for most of the time, then shot up to 1.6mg/s for a while. It’s officially installed and seems to be working now.
Now that’s solved, I still have a question relating to my overall goal to upgrade to fedora 39. Do any of you have any guidance on this question?