Computer Configuration > Administrative Templates > Microsoft Edge > Content settings
Both
HKLM\Software\Policies\Microsoft\Edge
Allows you to set whether users can add exceptions to allow mixed content for specific sites. This policy can be overridden for specific URL patterns using the 'InsecureContentAllowedForUrls' (Allow insecure content on specified sites) and 'InsecureContentBlockedForUrls' (Block insecure content on specified sites) policies. If this policy isn't set, users will be allowed to add exceptions to allow blockable mixed content and disable autoupgrades for optionally blockable mixed content. Policy options mapping: * BlockInsecureContent (2) = Do not allow any site to load mixed content * AllowExceptionsInsecureContent (3) = Allow users to add exceptions to allow mixed content Use the preceding information when configuring this policy.