Here's a link to my complete article:
Where is Ruby Installed on Mac
Below is a summary of the article.
To find out where Ruby is installed on macOS, use the `which ruby` command in the terminal. Entering the command `which -a ruby` will show you if more than one Ruby version is installed. If Ruby is not installed, the `which ruby` command will show you Ruby is not found. See the article Where is Ruby Installed? for details.