Comment by jeremy_k

Use asdf (https://asdf-vm.com/) to manage your Ruby versions.

You should be able to do

$ asdf plugin add ruby

$ asdf list all ruby (you'll see 3.4.1, the latest is available)

$ asdf install ruby 3.4.1

And now you can use Ruby 3.4.1 with no issues. Follow that up with

$ gem install bundler

$ gem install rails

$ rails new ...