Thank you, #12 fixed my issue. Uninstalled CKEditor 5 and run the update and it worked.
I'm having the same issue updating from Drupal 10.1.7 to 10.2.1.
All of my sites have been updated successfully, apart from one of them.
The update runs and gets to update 3 of 21 and stops. When I try to go back into run update.php it now gets stuck on 'starting updates' and hangs there forever.
I've tried clearing caches, running cron, updating entites and nothing seems to fix this.
Recent logs state the following after running update.php:
PHP Error:
Error: Call to a member function getConfigDependencyName() on null in Drupal\editor\Entity\Editor->calculateDependencies() (line 127 of /var/www/vhosts/csbdesign.co.uk/cessaha.co.uk/core/modules/editor/src/Entity/Editor.php)