With FAT32 images, copying files to an unmounted image is possible with the mcopy command:
mcopy -v -i [image file] -s [files to copy] ::/
However, this is not possible with an ext4-based image file. Is there an equivalent command to achieve the same result for an ext4-based image file? Mounting is not an option due to the image build tool (Yocto) being used not having sudo access.