Because the standalone Java application is considered legacy, you have two primary ways to access discovery functionality: Ubiquiti Device Discovery Tool (Chrome Extension):
The Ubiquiti (UBNT) Device Discovery Tool is a legacy utility used to find and manage Ubiquiti devices on a local network. While version 2.5.1 was a popular standalone release, it has largely been superseded by more modern alternatives Ubiquiti Community Download Options
mobile app, which offer more robust discovery and management features. Ubiquiti Community version instead? UBNT Discovery Tool V2.5.1 and JAVA on windows 10