Comment by iamnothere

As an observer and occasional Genode user, not a Genode developer, the non-Linux option with the highest development focus is the NOVA microkernel (default for Sculpt OS), with seL4 also receiving a lot of attention. Genode on Linux is most often used for development. I am not clear on the tradeoffs between different kernels but you may ask in the forums if interested. I suspect that the (formally verified) seL4 fully works, but at a performance cost.