Computer Configuration > Administrative Templates > Microsoft Edge > Identity and sign-in
Both
HKLM\Software\Policies\Microsoft\Edge
Configure this policy to decide whether WAM is used for authentication in Microsoft Edge on Windows 10 RS1 and RS2. If you enable this setting, WAM will be used in the authentication flow on Windows 10 RS1 and RS2. If you disable or don't configure this setting, OneAuth libraries will be used instead of WAM on Windows 10 RS1 and RS2. Note that if this policy is enabled, then previous sign-in sessions (which used OneAuth by default) cannot be used. Please sign out of those profiles. This policy will only take effect on Windows 10 RS1 and RS2. On Windows 10 RS3 and above, WAM is used for authentication in Microsoft Edge by default.