Genode is more an "OS construction kit" than an OS, isn't it?

Yes; but the project includes "Sculpt" which is more of an OS.

https://genode.org/download/sculpt

It has a distribution, Sculpt[0].

Many stories around using Genode in the Genodians[1] blog.

0. https://genode.org/download/sculpt

1. https://genodians.org/