Computer Configuration > Administrative Templates > Microsoft Edge > Content settings
Both
HKLM\Software\Policies\Microsoft\Edge
Create a list of URL patterns to specify sites that aren't allowed to display blockable (i.e. active) mixed content (that is, HTTP content on HTTPS sites) and for which optionally blockable mixed content upgrades will be disabled. If you don't configure this policy, blockable mixed content will be blocked and optionally blockable mixed content will be upgraded. However, users will be allowed to set exceptions to allow insecure mixed content for specific sites. For detailed information about valid url patterns, see https://go.microsoft.com/fwlink/?linkid=2095322. Wildcards (*) are allowed. Example value: https://www.example.com [*.]example.edu