With today's release of the Windows 10 (21H1) May 2021 Update, you now download the Windows 10 21H1 ISO for the operating system directly from Microsoft.

Learn how to download a Windows 10 ISO file without using the Media Creation tool with this step-by-step guide.

However, I plan to install Windows 10 onto a virtual machine using my newly created ISO file and then upgrade that VM to Windows 11. It should be an interesting experiment.