My machine has simply capped at ruby version 2.5, ruby -v outputs ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux-gnu]. I have tried sudo apt update && sudo apt upgrade, and sudo apt-get install ruby-full, but non of which have seemed to work.
The supported version is usually not up to date.
A common way is using any of those Ruby version management tools, such as:
Here is the list of ruby version management tools on the official site.
If this isn't what you aren't looking for, try to install the Ruby from source.
Lastly, you can use a Ruby Docker image to run the Ruby script.