I only see a .pkg file when restoring from DMG in TransMac. What is wrong?
I found a quicker and easier way to do this, so I'll share it here.
I found a website called https://bootableinstaller.com/, and it works like magic. If you run the script (Included with download), it converts the installer DMG into a bootable ISO.
As for my original problem:
It looks like I tried to flash the installer DMG without unpacking the .PKG file properly. The script mentioned above does that for me.