In answer to this message and for general information:
After searching the web and asking MistralAI and ChatGPT (and correcting them after having read the sources, beware they really can missunderstand/missinterpret things), it indeed seems that only companies in Japan and China are not using Jibe/Google for managing RCS.
Even Deutsche Telekom, which built its own RCS infrastructure, is collaborating with Jibe/Google for a wider coverage and more compatibility.
So, to my understanding, RCS = Google 