Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
OBSOLETE: This policy is obsolete and doesn't work after Microsoft Edge 105. This policy doesn't work because Discover is now contained within the Edge Sidebar and can be managed using the 'HubsSidebarEnabled' (Show Hubs Sidebar) policy. This policy lets you configure the Discover feature in Microsoft Edge. Working in the background when enabled, this feature sends URLs to Microsoft Bing to search for related recommendations. If you enable or don't configure this policy, you can use the Discover button on Microsoft Edge to start using this feature. If you disable this policy, you can't use the Discover feature in Microsoft Edge.