Okay, what seems to provide a drama-free installation on Win10 is this sequence:
Create and activate a fresh conda environment.
Run these commands in the new environment:
conda install -c conda-forge cartopy
pip install holoviews geoviews hvplot datashader
conda install -c conda-forge notebook
pip install $YOUR_OTHER_MODULES
Do not install holoviz from pip.
I’ll start playing with the visualization modules tomorrow. Thanks!