If you specifically need a .dmg file (e.g., for a virtual machine or a bootable drive), you must create it manually from the .app file you just downloaded: (Applications > Utilities).
Double-click the downloaded .dmg file to mount it, then run the .pkg file inside to extract the "Install macOS" app to your Applications folder. Macos Catalina Dmg Direct Download
softwareupdate --fetch-full-installer --full-installer-version 10.15.7 If you specifically need a
Catalina replaces iTunes with three apps. To fetch back the “Device” sidebar: Macos Catalina Dmg Direct Download