Core updates prior to 9.4.0, 9.4.4 for CKEditor, have been removed

All Drupal core updates added prior to the 9.4.0, 9.4.4 for CKEditor, release have been removed from the 10.0.x branch.

This means that Drupal sites running 9.3.x or earlier versions, must first update to 9.4.0 or later, prior to updating to Drupal 10. In general, sites should aim to update to the most recent release of their current major branch before updating to the next major release.

The Drupal 9.3.0 test database fixtures have been removed from Drupal 10, these have been replaced with new fixtures starting from 9.4.0.

Drupal 9.4.0 and 9.3.0 fixtures are available in Drupal 9.5.x so that contrib modules can write upgrade path tests that run against both major versions.