Defer updates will prevent users from seeing the Monterey update in System Prefs/Software Updates.
Create a configuration profile with the Restrictions payload - Functionality tab - select Defer updates of Only major software updates for 30 days and scope for all computers. Then scope exclusions for test computers or early adopters.
I was able to find a workaround to defer macOS Monterey with a plist instead of a full Restrictions Payload. This is EXTREMELY helpful, as you do not have to enable/disable any other settings in your environment with that configuration profile. I have this config profile scoped to a smart group of OS is Big Sur or higher.
For any devices on 10.15.7 Catalina or lower, you can still use softwareupdate --ignore "macOS Monterey". I found with my policy, the command is a bit finicky and did not apply properly to all machines. It seems a machine reboot, or flushing and re-pushing the command works if it fails the first time around.