Why is library(Seurat) causing my R session to have a fatal error?
If you haven't already done so I would make a complete installation of Anaconda, particularly good with bash. The I would either install using Anaconda Navigator, or ...

# Create an R environment and activate it
conda create -n r_env r-essentials r-base python=3.7
conda activate r_env

# install Reurat
conda install -c bioconda r-seurat

# installing standard packages
conda install -c r r-randomforest --yes


If you have a Mac the instructions are here. In some systems you need to just activate r_env . 

Please note if you've installed e.g. python3 with pip a conflict occurs with the Anaconda package.