Download the USB installer on macOS X Catalina I'm trying to download the USB installer of macOS X Catalina but I'm getting an error:

Update not found The requested version of macOS is not available.

I'm already on mac os Catalina 10.15, I'm not trying to update, I want to download the USB installer.

Below the error I'm receving, a screenshot and a gif.
softwareupdate --fetch-full-installer --full-installer-version 10.15

See also How can I download an older version of OS X/macOS?