Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
Enable this policy to let Google Cast connect to Cast devices on all IP addresses, not just RFC1918/RFC4193 private addresses. Disable this policy to restrict Google Cast to Cast devices on RFC1918/RFC4193 private addresses. If you don't configure this policy, Google Cast connects to Cast devices on RFC1918/RFC4193 private addresses only, unless you enable the CastAllowAllIPs feature. If the 'EnableMediaRouter' (Enable Google Cast) policy is disabled, then this policy has no effect.