Upgrade and deploy a Ruby on Rails project

We have a Ruby on Rails project using Ruby 2.3.1 and Ruby on Rails 4.2, and would like to get it upgraded to a currently supported version of both and deployed onto a new ubuntu 20.x server in AWS. Ideally we would also like to templatize the project deployment. We would also consider using a docker / kubernetes style deployment model that can elastically scale.

We'll want documentation and pre-planning throughout the process so we can take over management of it and build on the progress from the upgrade.