Change Ruby version with RBENV

Check versions installed on your machine:

rbenv versions

Install a specific version to your machine:
(replace 3.1.2 with the version you want to install)

rbenv install 3.1.2

Install the latest stable version of Ruby:

rbenv install -l

Set the Ruby version of a specific application by navigating to the app directory:
(replace 3.1.2 with the version you want to use)

rbenv local 3.1.2

Set the global Ruby version:
(replace 3.1.2 with the version you want to use)

rbenv global 3.1.2

This changes the Ruby version that will be used where a local version has not been set.