the 5.4. x is the current LTS release and ・ out Firmware 3.9. updates up to 5.4.11. states 5.4.x is LTS, 5.5.x is experimental, 5. Ubiquiti Community UniFi 5.4.11 Stable has been released - Ubiquiti Community
UniFi Controller is a network management software that allows users to configure, monitor, and manage their UniFi devices from a single interface. It provides a comprehensive set of features, including: unifi-installer.exe 5.4.11