Those remotes use a specific USB driver in order to work on macOS. The Harmony 1000, 1100, and 900 remotes were launched in 2006 and late 2009 respectively. If you have a remote that doesn't use a hub, you may download the latest software using the links on this page.
You can also continue to use MyHarmony on a computer running Windows or macOS 10.14 or lower. If you’re using a hub-based remote, you will need to use the Harmony app on your iOS or Android device.
32-bit software such as MyHarmony and Logitech Harmony Remote legacy software will no longer run on macOS 10.15 & above (Catalina/Big Sur/Monterey).