Defender Notifications - Annoying - But possible solution

I have been constantly asking on a solution here or searching for solutions elsewhere on how to disable or prevent Defender Security Intelligence Updates to run without those annoying notifications when Windows Update settings are set to Notify to Download and Install. Hopefully this setting should suppress the Defender notifications that come along with the Windows Updates.

Allow security intelligence updates from Microsoft Update (admx.help)

on how to disable or prevent Defender Security Intelligence Updates to run without those annoying notifications when Windows Update settings are set to Notify to Download and Install

I am wondering if you actually mean - to disable or prevent - updates to run without
or how to enable updates to run without etc.

However I only mention that as I am unsure of what you are trying to do.
Re the registry -
Registry Hive HKEY_LOCAL_MACHINE
Registry Path Software\Policies\Microsoft\Windows Defender\Signature Updates
have you actually tried finding that key on your registry as I have a feeling you will not actually find it as shown
I have a feeling it is to be found in a slightly different named key - security intelligence updates

My main reason for posting is that IMHO changing the primary source of such updates, is not a good idea.

The primary source presuming you are referring to Windows 10 standalone computer is Windows Updates.

When that is left as is, an update is configured with a certain degree of logic - this ensures the update is the one required and to some extent may limit the size of the update.

Not only that, but it also ensures that before OTHER windows updates are installed the correct updates to Windows Security Centre are also installed .

There are reasons why the source of updates to defender - in its widest terms - may be configured for other than windows updates - but IMHO none of them relate to the standalone home computer.

Check the settings in Start menu > Settings > System > Notifications & actions

igdat
I agree 100% - - if your suggestion or mine below works and I have no idea if it will - far safer than trying registry changes.

Settings - update and security - virus and threat protection settings
notifications