Previously, Appium Desktop bundled the server and the element inspector into one package. For Appium 2.0 and beyond, these have been separated to allow for a more modular, "platform" approach. Appium-Related Tools - Appium Documentation
Finding the "Appium 2.0 GUI download" is a bit different than it was for Appium 1.x. In the latest ecosystem, the monolithic has been deprecated. To get a GUI experience with Appium 2.0, you now download the Appium Inspector as a standalone app and use it alongside the command-line server . The Shift from Appium Desktop to Appium Inspector appium 2.0 gui download