I created a new Rails app (v5.2.4.3) using Ruby 2.7.1 and discovered the blizzard of "keyword parameter" warnings endemic in this release.
rbenv install --list, for some reason, doesn't list Ruby versions beyond 2.4.0. I've manually installed 2.6.6 but am unable to launch it.
This seems like a simple problem. Hints?
You should firstly check the version of plugin 'ruby-build':
cd ~/.rbenv/plugins/ruby-build
git log
If you have not ~/.rbenv/plugins directory, maybe it is too old for the version of your rbenv. First update rbenv:
cd ~/.rbenv
git pull
Then install 'ruby-build' plugin:
git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build