Yes, but the UDM must have “Layer 2 Discovery” enabled in its settings.

Introduction If you manage a network that includes Ubiquiti devices—such as UniFi access points, EdgeRouters, airMAX radios, or ToughSwitches—you know that finding devices on a flat or misconfigured network can be a nightmare. This is where the UBNT Discovery Utility comes to the rescue.

No – it’s a desktop tool. Ubiquiti offers the “WiFiman” mobile app for discovery on Android/iOS.