Computer Configuration > Administrative Templates > Microsoft Edge - Default Settings (users can override)
Both
HKLM\Software\Policies\Microsoft\Edge\Recommended
Allow Microsoft Edge to issue a connection to a web service to generate URL and search suggestions for connectivity issues such as DNS errors. If you enable this policy, a web service is used to generate url and search suggestions for network errors. If you disable this policy, no calls to the web service are made and a standard error page is shown. If you don't configure this policy, Microsoft Edge respects the user preference that's set under Services at edge://settings/privacy. Specifically, there's a **Suggest similar pages when a webpage can't be found** toggle, which the user can switch on or off. Note that if you have enable this policy (AlternateErrorPagesEnabled), the Suggest similar pages when a webpage can't be found setting is turned on, but the user can't change the setting by using the toggle. If you disable this policy, the Suggest similar pages when a webpage can't be found setting is turned off, and the user can't change the setting by using the toggle.