Downloading as a DMG file is primarily done through official Apple Support channels, especially if you are using an older Mac that is compatible with this version. 1. Official Download from Apple

Modern hardware configurations running Apple Silicon (M1/M2/M3) or modern versions of macOS actively block legacy installer execution policies.

Apple hosts legacy installers explicitly via direct web browser links. You must use the Safari browser on a compatible Mac for the direct download to process correctly.