On the global settings screen, if you add extra notification emails, you can delete them.
But you can’t delete the first default one. If you delete it and save settings, it comes back.
It should be deletable, and deleting it should disable all dashboard-generated emails.
I know there’s a snippet to do this, but disabling emails is a fairly basic feature. Also, having a delete button that appears to work but then has no effect, is rather poor usability.