Drupal 8 to 9 was the easiest major Drupal upgrade in a decade! D10 is a similarly straightforward upgrade. The tools and processes to use to prepare are the same. Most of the upgrade steps involve keeping your Drupal 9 site all up to date with latest Drupal core and contributed projects.
We tracked the status of contributed projects based on data produced by the Drupal Association, like we did for Drupal 8 to 9. The latest update on Drupal 10 was presented by Gábor Hojtsy at Drupaljam on June 1, 2022. Check out this recording:
Drupal 9.4.0 defined all the deprecated APIs for Drupal 10, so it is time to get prepared for the new major version.
- Upgrade to Drupal 9 if not already. The tools only support code compatibility checking towards the next major version, so you must be on Drupal 9 for accurate upgrade status information.
- Install Upgrade status on your development site.
- Use the Administer >> Reports >> Upgrade Status page to check if there are contributed modules you can update to get compatible and to learn about the deprecated API uses you can fix in your custom code. Use the latest Drupal 9 release to check to make sure all deprecated APIs are detectable.
- Contributed projects receive help from the Project Update Bot to be compatible. You should use drupal-rector to automatically fix various issues in your custom code. Upgrade Status will help to identify where to do what.