Most websites consist of basic text and images but to add equation to websites some extra tools are required. In Drupal 9 two such tools are available: MathJax and Equation Editor.
The next step will be to add some coding stuff to this website. It would be nice to add code highlighting first for better readability. Drupal 9 currently has three modules that offer code highlighting: CKEditor CodeSnippet, Server-sided code highlighting and GeSHi Filter for syntax highlighting. GeSHi filter seems to lack support for two languages I need. Therefore, I went for CKEditor CodeSnippet.
It's impossible to write a Drupal module or fix bugs (issues) without some guidance. Some useful links for module development and issue handling are listed here.
Just some things I've experienced when I installed Drupal 9.