Why is softwareupdate --ignore not available anymore in Big Sur and Monterey MDM? This is horrible for enterprise environments.

Go to System Preferences>Software Update and uncheck Automatically keep my Mac up to date.

The Click on Advanced and make sure the items are unchecked. Software upgrades always required manual action.

Updates are dot changes to one macOS version like fro 12.3 to 12.3.1while upgrades are changes to macos version like from Big sur to Monterey.

For enterprises, they can You have to create a Configuration Profile using Apple’s Profile Manager or the full MDM suite to control many things including installing updates and upgrades.

Distribute profiles manually with Profile Manager - Apple Support

Create and edit configuration profiles in Profile Manager - Apple Support

Manage macOS updates with Mobile Device Management (MDM)