Firstly, I am not sure which distro's desktop you are running. But couple observations in this thread.
Vanilla v10+ is a WoofCE variant IIRC.
My experience with Vanilla v11+ is that it is a very good up to date using the same Pipewire-Wayland that the mainstream distros use, today. The author is forward-thinking in that regard over the past couple years. As such, has produced quality distros taking advantage of the Linux improvements over those same years to keep the creations equal to or ahead of worldwide improvements.
On the IMG issue, to expose its contents you have been given several manners to expose. @BarryK gave me one a few years ago but I cannot find his advice.
On QEMU, it will allow you to 'boot' either your v10+ ISO file OR your v11+ IMG file to a desktop. The ISO file can be opened and its contents manipulated via ISOmaster. Yet, I know of no such equivalent utility to do so with an IMG as its construct is immensely different. Either an ISO file or IMG file, both, are mere shipping containers for a bootable OS. Further, while it is reasonably simple to exchange contents of an ISO file with ISOmaster, to do the same in an IMG file requires a complete different manner to build/rebuild for a new.
I continue to use Ventoy as my holder of ALL of my bootable ISO files and IMG files. And from it I can boot, either, to desktop without issues. Same is true for QEMU as it will boot an ISO file or it will boot an IMG file OR it will boot my Ventoy USB containing my ISO & IMG files where I can select which of its files to launch to desktop.
No matter which method of getting to desktop, the problem still exist that you are experiencing. Namely none of the booted desktops allow you to interrogate the contents of an IMG file.
@dimkr's explanation, though, a little short in being clear is the best example for opening his IMG file(s). OR, if you find the answer Barry gave me awhile back, that follows the same logic to expose the contents of the IMG file that you appear to be seeking as, IIRC, his was simpler to visualize what to expect.
Hope this is helpful in the quest.