Hi @astralien3000,
The fork you referred to is available here.
RIOT was indeed considered as one of the candidates to build up a prototype of a ROS 2 microcontroller-oriented framework however the prototype was finally built on top of NuttX instead. The resulting prototype is available here.
The amount of time/effort put into that prototype was relevant so I’d encourage you to review the NuttX one before jumping straight to a new RTOS.