Drupal Module Upgrader (DMU) was created by Angie Byron and Adam Hoenich way back in 2014 at Acquia to help folks upgrade custom Drupal 7 modules to modern Drupal. It was magic. Cameron Zemek at PreviousNext built the crucial underlying library, Pharborist, which abstracted PHP manipulation into a generic dependency. Many relied on DMU to upgrade custom code, and it was even updated for Drupal 9; however, keeping it current over time proved challenging.