I updated my Windows 7 Home Premium yesterday. I was led to believe I would need a fresh activation key and could buy one from Ebay, but it activated without ever asking for the key. I think it just accepted my w7 key.

I followed these instructions: https://www.forbes.com/sites/gordonkelly/2020/01/15/how-to-upgrade-to-windows-10-for-free-in-2020/#28d780f4716a

(I had purchased a fresh w7 key on Ebay for less than $5, which is a lot cheaper than buying w10 for $130, but as I said it proved unnecessary)

By the way, it took more than 4 hours for my desktop computer to complete the installation. When they say it takes a long time, believe them and plan accordingly