My post doesn’t answer your question at all, but I suppose it can help you.
Take a look at this extension - Pointer Lock for Defold.
It doesn’t use DefOS. It has an example of a mouselook and an exceptionally simple 3d camera script. And check out my FPS game from the previous Ludum Dare (Oh, I promised to make an FPS template for Defold in the topic. I’m still working on it…)