ruby@2.7 is keg-only, which means it was not symlinked into /usr/local, because this is an alternate version of another formula.
libpq is keg-only, which means it was not symlinked into /opt/homebrew,
because conflicts with postgres formula.
See also
- Ruby, Sinatra, Ruby on rails, RubyGems,
gem, bundle, Rack, Gemfile, Keg-only, brew install [email protected], bundle, JRuby, CocoaPods, apt install ruby, Fog, Puma
- Homebrew,
brew, pkgutil, /opt/homebrew/, installation
