I recently asked in a comment on a howo-to video whether Windows ISO is available from an official source. Split-second later, I instinctively searched “windows 11 download” and the first result gave me the answer.
Yes, it is available from microsoft website.
Here is the link:
https://www.microsoft.com/en-us/software-download/windows11
So you can download the version appropriate for you and I was particularly interested in the third one that is an ISO image that allows one to create a bootable installation media.