FunKey-OS is a Linux operating system distribution developed for use on the FunKey S. The default application launcher of FunKey-OS is RetroFE, with the alternative Gmenu2X launcher also included. As FunKey-OS is open source, the distribution and its source files are both publicly available for download on the FunKey Team's GitHub page.
The default RetroFE-based FunKey-OS launcher separates and displays games loaded onto the FunKey S based on emulated system. Chosen for its simple layout and ease of use, RetroFE lists games with their names and associated box art images, if present. While more complex, the alternative Gmenu2x launcher provides additional options for customization, such as interchangeable backgrounds and support for third-party OPK programs. While RetroFE and Gmenu2x each have four themes included by default, additional themes can be added to FunKey-OS for further customization.