The last issue was due to an incompatibility between apple’s python that ROOT was built with and the python version used by Jupyter installed by mac ports.
Recompiling ROOT with the macports Python required setting the following two environment variables to get cmake to complete the configuration:
export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8
I then need to install the metakernel package.
The notebook now starts correctly and was capable of drawing a simple histogram.