A new version of the MutantC has been unveiled, the third of its kind. The handheld computer is highly versatile and can run on several SBCs. The MutantC v3 contains numerous improvements on its predecessor, including a buzzer and a real-time clock.
https://www.notebookcheck.net/MutantC-v3-Updated-open-source-handheld-computer-with-a-slide-out-keyboard-announced.519393.0.html