If the installer starts automatically, quit it to keep the file for your DMG creation. 2. Direct Download via Terminal
A legitimate 10.15.7 DMG inside the app will yield a specific hash (Apple does not publish these publicly, but community sources confirm 19H15 is the golden master). Download Macos Catalina 10.15.7 Dmg File
Apple hides older OS versions from accounts that never "purchased" them. Use the Terminal command provided in Part 3; it bypasses this restriction. If the installer starts automatically, quit it to