Google Cast must be disabled.

Enable this policy to enable Google Cast. Users will be able to launch it from the app menu, page context menus, media controls on Cast-enabled websites, and (if shown) the Cast toolbar icon.

Disable this policy to disable Google Cast.

By default, Google Cast is enabled.

The policy value for "Computer Configuration/Administrative Templates/Microsoft Edge/Cast/Enable Google Cast" must be set to "disabled".

Use the Windows Registry Editor to navigate to the following key: HKLM\SOFTWARE\Policies\Microsoft\Edge

If the value for "EnableMediaRouter" is not set to "REG_DWORD = 0", this is a finding.

Set the policy value for "Computer Configuration/Administrative Templates/Microsoft Edge/Cast/Enable Google Cast" to "disabled".