Ok, just to make sure I understand this correctly. - This is basically a commercial smartwach (the Colmi P8) that is based on a well documented SOC, the nordic nRF52832 - The open source version comes with an enclosure that is not glued shut, so that it is easy to access testpoints on the pcb. - Development is done by accessing the nRF51 SWD interface with pogo pins or similar. The programming interface can be a stan…
https://tinygo.org/microcontrollers/pinetime/
With that, you can write Go code which (when compiled) is then flashed to the watch for running directly on the hw. No need for an OS layer underneath.