There are surprisingly few tools to work on file system images in the Linux world, they expect loopback mounting to always be available.

There are a few libraries to read ext4 but every time I've tried to use one it missed one feature that my specific image was using (mke2fs changes its defaults every couple years to rely on newer ext4 features).

7-zip can also read ext4 to some degree and, I'm not sure but, they seem to have written a naive parser of their own to do it: https://github.com/mcmilk/7-Zip/blob/master/CPP/7zip/Archive...