We had some difficulties with configurations of Webpacker and Docker for autoreload. After some issue this configurations seems work very well.

# config/webpacker.yml
development:
  <<: *default
  host: webpacker
  hmr: true
  compile: true

  # Reference: https://webpack.js.org/configuration/dev-server
  dev_server:
    https: false
    host: webpacker
    port: 3035
    public: localhost:3035
    hmr: true
    # Inline should be set to true if using HMR
    inline: true
    overlay: true
    compress: true
    disable_host_check: true
    use_local_ip: false
    quiet: false
    headers:
      'Access-Control-Allow-Origin': '*'
    watch_options:
      ignored: /node_modules/