What you are referring to is the legacy protocol called UAVCAN v0, also known as DroneCAN. This forum is mostly dedicated to the next generation solution called Cyphal, formerly UAVCAN v1. The differences between the two are outlined in this article: Cyphal vs. DroneCAN
DroneCAN still requires the data type signature and it can be computed using this script: libcanard/show_data_type_info.py at master · dronecan/libcanard · GitHub. For further information I recommend contacting the DroneCAN maintainers directly.