Fuchsia is definitely not an RTOS, it's an embedded system of sort. I had some experience with little kernel which served the basis for zircon, so I followed the project for a bit - they have no real time guarantees from what I could tell.
Little Kernel? I mean yes, that was designed for embedded, but Google has rewritten a lot of it. What makes you think that it can’t be used for other things now?
