Information
This setting allows Microsoft Edge to issue a connection to a web service to generate URL and search suggestions for connectivity issues such as DNS errors.
If this policy is enabled, a web service is used to generate URL and search suggestions for network errors.
If this policy is disabled, no calls to the web service are made and a standard error page is shown.
If this policy is not configured, Microsoft Edge respects the user preference that is set under Services at edge://settings/privacy. Specifically, there is a 'Suggest similar pages when a webpage can't be found' toggle, which the user can switch on or off.
Note that if this policy has been enabled (AlternateErrorPagesEnabled), the 'Suggest similar pages when a webpage can't be found setting' is turned on, but the user cannot change the setting by using the toggle.
If this policy is disabled, the 'Suggest similar pages when a webpage can't be found' setting is turned off, and the user cannot change the setting by using the toggle.
Solution
Set the policy value for 'Computer Configuration/Administrative Templates/Microsoft Edge/Suggest similar pages when a webpage can't be found' to 'Disabled'.