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.
Great strides have been made in the Drupal core Media Initiative, which promises an improved authoring and content management experience. What used to require a number of contributed modules and custom setup can now be accomplished by using 8.8+ core alone.
Among the better options is Prism.js, which in addition to being lightweight code-wise, gives a number of options on how you may wish to present code. Furthermore, if you need to remove it from your project at a later time, your underlying content won't be affected.
Drupal underwent a sea change moving from 7 to 8. Although the stock administrative interface and site building concepts will look familiar to long-time users, much is different beneath the surface. This requires a different approach to site building and management for your Drupal projects.
Following are tips for standing up a Drupal 8 site locally for test and evaluation, as well as some guidelines for running a complete build. The code instructions are geared for Unix-based systems such as MacOS or Linux, but can be adapted for Windows.