In macOS 10.13, if you use Disk Utility to create a new image from a folder, it will be APFS formatted.
These images can only be read on 10.12 or newer, and there’s no option to pick a different format in the GUI.
Instead you can use hdiutil in Terminal make a folder into an HFS+ disk image:
hdiutil create -srcfolder /my/folder -fs HFS+ /my/image.dmg
When adding Epson EasyMP Multi PC Projection 2.1.0 to Munki, I found that the built-in postinstall script fails.
Some digging revealed that the script was expecting a file to exist at </tmp/mpp-72B3FDFF-9513-4CED-96C3-34881FC77AB8>. It reads that file and uses the value contained for the “ClientMode” preference in </Library/Preferences/com.epson.EasyMP_Multi_PC_Projection.Settings/mppsettings.xml>
On a successful install the the GUI, that preference is just the integer “0”. So I added the following preinstall script to my Munki pkgsinfo.
echo "0" > /tmp/mpp-72B3FDFF-9513-4CED-96C3-34881FC77AB8
The postinstall script is appeased and EasyMP Multi PC Projection 2.1.0 installs successfully. No direct modification or repackaging necessary.