The Gboard double-sided version directory contains the firmware and hardware designs for the product, released on Oct 1, 2024, although it is not an officially supported Google product. The files included are for case design, schematics, PCB layouts, firmware resources, and more. Surprisingly, users need to prepare 3D printed parts, build multiple boards, and connect them in specific configurations while following detailed instructions. The firmware upload process is complex, requiring specific steps for each type of board. To develop the firmware, users must install specific tools and follow detailed compilation and upload steps. Remember to check licensing information as well.
https://github.com/google/mozc-devices/tree/master/mozc-doublesided