Since the installer comes as an App, you need to convert it into a disk image (DMG) and then into an ISO. We will use the for this process.
You now have a clean, unmodified HighSierra.iso suitable for: macos high sierra 10136iso
For enthusiasts and users of "vintage" hardware, the 10.13.6 installer is the gold standard. It provides the most modern web standards and security possible before these machines were officially phased out of the macOS ecosystem. Conclusion Since the installer comes as an App, you