Unfortunately the Citrix MAM SDK does not yet provide support for Microsoft Authenticator because it blocks the incoming tokens from the authenticator app.
Notate supports a work-around however that will allow you to continue to use the app without having to remove Authenticator from your device. In the Notate application policies on your Citrix server, make sure you set “Allow Microsoft Authenticator” to false. At that point, Notate will log in with Modern Auth, but will not request the token to be returned from the Authenticator app and Notate should log in successfully.