Updates. By Jeff Kreeftmeijer

iex(1)> :observer.start  
[error] ERROR: Could not find 'wxe_driver.so' in: /Users/jeffkreeftmeijer/.asdf/installs/[…]

The observer needs wxwidgets. Check with wx-config --version, install on macOS with brew install wxmac, then reinstall Erlang. #elixirquicktips