Some users repackage these VHDX files into ISO format using third-party tools. These are unofficial and often broken. For the "pure" experience, you want the VHDX, not a converted ISO.
If you successfully boot a build like 20279 from the archive, you will experience a highly sanitized version of Windows: windows 10x iso archive.org
In the VM settings, go to Security and uncheck "Enable Secure Boot" if the image fails to load. Some users repackage these VHDX files into ISO
This is Microsoft’s proprietary sector-based imaging format. FFU images are meant to be flashed directly to physical storage drives (like an eMMC or SSD) or loaded into specific emulators. you want the VHDX