You can no longer install Windows 10 with a 7/8 key

[mikemex]

Ugh. For years it was possible to upgrade from 7 to 10 for free with the factory key of old machines.

Since my X220 always ran Windows 7, I never bothered to activate Windows 10 on it, knowing that I could do that at any time (despite M$ claiming one year promotional period). And now, that I finally decided to give Windows 10 a go, I can no longer activate it.

It seems that a LOT of people were upgrading to Windows 11 using this path, so M$ became upset and permanently disabled it. This happened on September 20, 2023.

I'm not aware of any way around this. Might as well get a second hand W10 COA.

[RealBlackStuff]

Try the Micro Win 10 by Dark Reverser as mentioned here on a spare drive.
Once activated, you probably should then be able to install a 'regular' W10, OR W10 LTSC 2019/2021.

Come to think of it, maybe dump Micro$haft altogether and install Linux?