On macOS Catalina or earlier you still can use the "software update --ignore" command.
On macOS Big Sur you can use the new "com.apple.applicationaccess" preference keys to delay major OS updates for 90 days: set "forceDelayedMajorSoftwareUpdates" to true, set "enforcedSoftwareUpdateMajorOSDeferredInstallDelay" to 90.
On all versions of macOS you can create a Restricted Software entry in Jamf for "InstallAssistant". This prevents any user from running the Install macOS xxx application. However you can still call the startOSinstall command via Terminal.