If you need an ISO for a virtual machine (like VMware or VirtualBox) and cannot access a Mac, these community-vetted sources are common alternatives: Internet Archive
Apple no longer lists High Sierra prominently in the App Store’s "Updates" tab. However, Apple still provides official download links for older installers, hidden away in the support section. macos high sierra 10.13 6 iso download
Example:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyUSB --application-path /Applications/Install\ macOS\ High\ Sierra.app --nointeraction If you need an ISO for a virtual