See list of known installation packages
rvm list known

Then, install the specific version of Ruby that you need through RVM, replacing the highlighted version number with your version of choice, such as ruby-3.0.0 or just 3.0.0:

rvm install 3.0.0

After the installation, you can list the available Ruby versions you have installed by typing:

rvm list

You can switch between the Ruby versions by typing:

rvm use 3.0.0