If your current Mac shipped with a newer operating system (like macOS Ventura, Sonoma, or Sequoia), Apple may block you from downloading older versions via the App Store.
and use the createinstallmedia command to create a bootable drive: Download Macos 10.15 Catalina Dmg File
To install MacOS 10.15 Catalina from the DMG file: If your current Mac shipped with a newer
Once completed, a file named Install macOS Catalina.app will appear in your folder. Method 2: Downloading via the Terminal Download Macos 10.15 Catalina Dmg File
When trying to mount a DMG, you may receive an error that the resource is busy.
Keep a physical recovery drive on hand for troubleshooting computers without an active internet connection. macOS Catalina System Requirements
