While Apple no longer provides a direct DMG download on their main marketing pages, you can still access it through the Official Apple Support Page which provides a link to the Mac App Store for older OS versions.
The system will open the Software Update panel to begin downloading the installer. macos high sierra 10136 dmg
High Sierra dropped support for legacy software RAID. Solution: Backup data, break the RAID set using Disk Utility, then install. While Apple no longer provides a direct DMG
Your Mac will verify the hardware compatibility and begin downloading the installer to your Applications folder as "Install macOS High Sierra.app". Converting the .app to a .DMG File Solution: Backup data, break the RAID set using
Once the installer loads, use to erase your main drive (choose APFS for SSDs or Mac OS Extended (Journaled) for HDDs). Close Disk Utility and select Install macOS . Technical Specifications & Compatibility Size: Approximately 5.2 GB.