The Ionic version used in this project requires Node.js 14, because it has a dependency on a version node-sass that doesn't work on Node.js 16 (latest LTS).
Node.js 14 is still supported until 2023.
You can download Node.js from the following URL:
https://nodejs.org/download/release/latest-v14.x/
sudo rm -rf /usr/local/lib/node_modules
sudo tar vzxf node-v14.18.2-darwin-x64.tar.gz -C /usr/local/ --strip-components 1
(note: the version number of the latest version of Node.js may have changed, update the command line accordingly)