Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
This policy enables the default browser settings campaign. If a user clicks to accept the campaign, their default browser and/or default search engine will be changed to Microsoft Edge and Microsoft Bing, respectively. If the user dismisses the campaign, the user's browser settings will remain unchanged. If you enable or don't configure this policy, users will be prompted to set Microsoft Edge as the default browser and Microsoft Bing as the default search engine, if they do not have those browser settings. If you disable this policy, users will not be prompted to set Microsoft Edge as the default browser, or to set Microsoft Bing as the default search engine.