I'd start there and see if it can be used for 11 or upgraded through the versions. Then I'd take a "clean" backup and use that to re-install in the future, instead of a new ISO.
Don't ever run random scripts from the Internet unless you understand every line.
but do run scripts that have been verified by reputable sources
You can permanently activate it with the scripts from massgravel: https://github.com/massgravel/Microsoft-Activation-Scripts
Didn't microsoft recently push something to prevent these from working?
They recently broke hwid, but was recently fixed as of 2.2. The other method worked fine still
Personally, I'd never use one of these scripts.
Most PCs have a windows key burned in to the BIOS.
https://www.howtogeek.com/660517/how-to-find-your-windows-10-product-key-using-the-command-prompt/
I'd start there and see if it can be used for 11 or upgraded through the versions. Then I'd take a "clean" backup and use that to re-install in the future, instead of a new ISO.
Don't ever run random scripts from the Internet unless you understand every line.
but do run scripts that have been verified by reputable sources