Here is a summary of the provided text in one paragraph: To build and package a Flutter desktop app for macOS using Bitrise, you need to start by setting up your project on GitHub and then connecting it to Bitrise. You then select the "Flutter project" and choose the Xcode stack for macOS apps. Next, you configure code signing for your app with Bitrise and add steps to automate the build process, including installing pods, running the Flutter build command, building an Xcode archive, deploying to Bitrise.io, and creating a .dmg file. Once the workflow is set up, you can push your changes to GitHub, run the build, and download the .dmg file to install the app on your local machine. Additionally, you can create a .dmg file for your macOS app by using NodeJS and NPM to generate an AppDmg configuration file and then running the `appdmg` command.