Why won't Ventoy boot a Microsoft Windows 10 ISO file?

[Renatus]

You said 'so it boots from the MBR, doesn't need EFI partition for booting.'

If you make a fresh Ventoy USB drive, then partition 1 is completely empty - but you can Legacy boot from the USB drive to the Ventoy menu (which then reboots because the partition 1 is empty). The Legacy boot files are on Partition 2. It DOES need the EFI partition for Legacy booting.

Please can you add screenshots of standard Ventoy USB drive with the two Windows files in the Ventoy menu.
Then show screenshot of UEFI-booting 'good' ISO and screenshot of booting 'bad' ISO.

Also, try formatting first partition as NTFS.

I can boot the ISO OK (partition 1 = NTFS, older Ventoy than you).

Another explanation is that NUC is causing an issue. Can you boot on different systems as a test?

Hi Steve, sorry but you are wrong in relation the need to have a EFI partition to boot, you only need the MBR to boot in legacy mode, you can check here https://ventoy.net/en/doc_disk_layout.html in the MBR section.
In old or legacy systems, EFI partition never existed and in fact is not needed, only when EFI was introduced by Intel, a new partition EFI, was needed for the system to boot, Ventoy allows both methods to work.
I tried as you suggested booting on another system, this time on a ASUS Deskmini X300, this system only allows UEFI booting, not legacy booting, and in fact it works with the same ISO that doesn't work in the NUC when I use UEFI booting, in both cases as expected the systems boot from the second partition.
So, it seems the NUC is the culprit, and that's odd, because the NUC is an Intel PC and it was Intel that invented the EFI specification.