Converting Older Drupal 8 Sites to 8.8 and Preparing for Drupal 9
Due to the quick change of pace in Drupal, documentation can sometimes struggle to keep up. Here’s an abbreviated method for updating an older install of Drupal 8.x that uses drupal-composer/drupal-project (a common framework) to drupal/recommended-project, for use with 8.8+ and 9.0+ projects. I've successfully run this on a few of mine.