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.
While both of FunKey-OS's application launchers are similar in that they divide games by emulated system, display associated box art images if present, and are customizable with various themes, each launcher has its key distinguishing advantages. RetroFE, the default FunKey-OS launcher, allows users to scroll through the system's library of emulated consoles, with each system's games also being navigable via a scrolling menu. While this simple and intuitive game navigation system is what gave the launcher its default status, it also gives it the weakness of being less flexible and customizable than the alternative Gmenu2x. In contrast, while Gmenu2x has the advantages of wallpaper customization and third-party application support, its more traditional application navigation system of icons divided into sections makes it more complicated to navigate than RetroFE. While RetroFE and Gmenu2x come with six and four default themes, respectively, additional themes can be added to the device for further customization.
While the comparatively low hardware specifications of the FunKey S leaves FunKey-OS without many of the typical applications and functions a user might expect from an operating system, such as a web browser or USB host capabilities, it still remains quite versatile. Including Commander, a file management program, by default, users can also install calculator, media player, and terminal programs on the emulation-focused device to give it additional functionality.