Further down, discussing bare metal (clean) installs:
No, this scenario is applicable only if you already installed Windows 10 and it has been activated.
You won't be able to use Windows 10 product key to activate Windows 11 this way and it is only possible if Windows 10 already been installed and activated.
As a workaround, you may install Windows 10 and activate it and then upgrade to Windows 11.
Looks like you would still need to use a workaround for it.
In the end I found a Windows 11 pro OEM key for $15 and picked one up. Same place I bought my last Windows 10 pro OEM key from.
Have got most items backed up and am getting ready, will probably start the process next week while I'm off work and after the holiday. There will need to be some changes in the BIOS for this to install, enabling UEFI and secure boot I'm assuming. Will need to research a bit more.
Some of my apps (logitech ghub, corsair icue, nzxt cam, etc.) don't have explicit windows 11 support so this should be interesting.. There may be some issues with those.