hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina
Apple doesn't provide a direct "DMG" link on their website; instead, they provide an .app installer via the Mac App Store. 100% secure, signed by Apple, free. download macos catalina 10157 dmg file better
Since Apple provides the installer as an .app bundle, you might need to convert it to a .dmg for use in VirtualBox, VMware, or for archiving. hdiutil attach /tmp/Catalina
Before you install, ensure your Mac is on the compatibility list: Early 2015 or newer MacBook Air/Pro: Mid 2012 or newer iMac: Late 2012 or newer Mac mini: Late 2012 or newer signed by Apple
If you are on a Windows PC and cannot use the methods above, you may look for mirrors on sites like Archive.org .