A few hints about setting up an Introduction Package based TYPO3 v7 installation with Composer, Docker CE including Docker Compose and DDEV. I guess this could be helpful for those who still have to do bugfixing and development with the more or less outdated TYPO3 v7. My operating system is Linux Mint 19.1 Tessa MATE (64-bit). Things might vary on other systems.
Packagist provides the Introduction Package only in version 3 or higher. TYPO3 v7 though requires version 2 which is available only via [TYPO3 Extension Repository](https://extensions.typo3.org/