.img file structure

[measter]

Current Ventoy handles some .img packages just fine but not others, which is acknowledged in the doc/s.  I would like to learn more about the differences, how to examine an .img for information.

Example of a usable .img with Ventoy is now Easy OS:  
https://distro.ibiblio.org/easyos/amd64/...23/5.4.10/

Example of an .img which is not usable by me in any way I have discovered is Armbian for x86 (not ARM, I understand that).
https://fi.mirror.armbian.de/dl/uefi-x86/archive/

[measter]

I would like to learn more about the differences, how to examine an .img for information.

I'm learning some by using command fdisk -l and by using the graphical gnome-disk-utility function of disk image mounter.  The Easy OS 'makes sense' to me; the Armbian not so much in the disk image mounter.