There are archives (such as the well-known "Mints" archives or Internet Archive) that host pre-made DMG files of High Sierra.
Q: Is it safe to download and install macOS High Sierra from a DMG file? A: Yes, it is safe to download and install macOS High Sierra from a DMG file, as long as you download it from a trusted source like Apple. macos high sierra download dmg install
Here’s a concise guide covering macOS High Sierra DMG download and installation. There are archives (such as the well-known "Mints"
The .pkg above extracts to a real installer. A raw .dmg of the full OS is rare. Most users want the Install macOS High Sierra.app inside the .pkg . macos high sierra download dmg install