Jupyter in gentoo is python only. We should add julia kernel.
Actually julia support in jupyter is provided by IJulia. This can be installed with julias own package management system, see https://github.com/JuliaLang/IJulia.jl/blob/master/README.md#installation. I don't think there is a clean way to get this into an ebuild. Btw, it is not python only, e.g. in the science overlay we provide a metakernel modules for bash ;)
Yes - getting julia support in jupyter is a simple matter of installing the corresponding IJulia package: - setting JUPYTER environment variable julia> Pkg.add("IJulia") and possibly registering the jupyter kernel.