title: How to use Ruby 2.6.6 when rbenv can't find it?
body: <p>I created a new Rails app (v5.2.4.3) using Ruby 2.7.1 and discovered the blizzard of &quot;keyword parameter&quot; warnings endemic in this release.</p>
  <p><code>rbenv install --list</code>, 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.</p>
  <p>This seems like a simple problem. Hints?</p>