Once you have the "Install macOS [Version].app" in your Applications folder, follow these Terminal steps to convert it into a bootable ISO: How to download and install macOS - Apple Support (IN)
For older versions (El Capitan, Sierra, High Sierra, Mojave), Apple provides direct download links via its support site. However, these are .dmg or .pkg files, not ISO. mac os download iso
: hdiutil attach /tmp/macOS.dmg -noverify -mountpoint /Volumes/macOS Once you have the "Install macOS [Version]