Instead:
macOS Catalina 10.15.7 ISO Download: Build a Reliable Installer macos catalina 10157 iso download new
This is the most straightforward and recommended method if you have access to a working Mac. Instead: macOS Catalina 10
If you have downloaded the official installer from the App Store, you can create your own ISO using Terminal: Create a blank disk image macos catalina 10157 iso download new
Once you have the full installer in your Applications folder, open Terminal and follow these steps precisely.
: Ensure your hardware supports 10.15.7 before starting.