"/Applications/Install macOS Sonoma.app does not appear to be a valid OS installer application."

Very often, the installer for when you haven't upgraded to the new OS will be a partial installer. It does not contain the necessary components to create an installer.

You might be able to download a full installer with this command:

softwareupdate --fetch-full-installer --full-installer-version 14.0

So, the solution is to delete the install Sonoma app from applications and use the software update command to redownload the corrupted file.

softwareupdate --fetch-full-installer --full-installer-version 14.X.X

change to the version you need as long as it is a full install version.

Then use the standard commands as per the Apple Support site.

Tried deleting and re-downloading the Sonoma installer from Apple, using Safari to download it?

Does the following command show the expected help text?

/Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia

skategeezer1965 wrote:

So, the solution is to delete the install Sonoma app from applications and use the software update command to redownload the corrupted file.

Yes, that’s what I said earlier. The installer isn’t corrupted by the way. It just isn’t designed to make a USB installer.

if you have not upgraded, then you get an “upgrade” installer. You cannot get a full installer from the App Store until you have upgraded the OS.