This does not produce a pure ISO, but it gives you a physical installer drive.
sudo shasum -a 256 /Applications/Install\ macOS\ Ventura.app/Contents/SharedSupport/SharedSupport.dmg macos 13 ventura image download
This guide covers everything you need to know about downloading the macOS Ventura image, creating bootable drives, and preparing files for virtualization. This does not produce a pure ISO, but
Only trust the official installer from Apple’s servers or your own creation from that installer. creating bootable drives
Typically, Apple keeps the last two major macOS versions available. Ventura will likely remain downloadable via softwareupdate until late 2025, but it may disappear from the "Purchased" tab of the App Store. Download and archive your image now.
This is the exact solution for the keyword "image download."