Hi Vladimir,
I think there is nothing wrong with having the Jupyter-related files for ROOT in /etc/root/notebook/, including the kernel. When the user runs “root --notebook”, these files will be made available to Jupyter, so no need to do any copy, one can just work with “root --notebook”.
Moreover, only the users that actually invoke ROOT will find their ROOT C++ kernel in the Jupyter list (plus other ROOT-related customisations of Jupyter), while this won’t show up for those that might be interested in working with different kernels of Jupyter (which they might have installed in $HOME/.local).
Cheers,
Enric