Alternative ways to defer major macOS upgrades on Tahoe

Hi Team,

I am reaching out to inquire about alternative methods for deferring major macOS software updates on our managed fleet, specifically for devices currently running macOS 26 (Tahoe).

We previously relied on standard configuration profiles using the forceDelayedMajorSoftwareUpdates and enforcedSoftwareUpdateMajorOSDeferredInstallDelay keys to enforce a 90-day delay for major OS upgrades.

We understand that with macOS Tahoe, Apple has deprecated these keys in favor of DDM using the com.apple.configuration.softwareupdate.settings payload and the MajorPeriodInDays key.

However, we are currently facing a limitation with our MDM provider (Endpoint Central), their platform does not currently allow us to upload raw JSON DDM payloads, and they have not yet updated their UI to natively support the new DDM software update keys.

Given this limitation, we are looking for alternative, officially supported ways to block or defer the upcoming major release (macOS 27) for 90 days. Specifically, we would like to know:

1. Are there any local defaults write commands or scriptable methods that can enforce a major OS deferral on macOS Tahoe?
2. Is there a temporary fallback profile or supported network-level URL blocklist we can implement to prevent the system from seeing the major upgrade while still allowing minor/security updates?

Thanks in advance.