So, like Icarus, I flew too close to the sun, and fucked up. I was trying to upgrade a small site from Drupal 9.3 because something under the hood was stopping image files from uploading. Unfortunately, I didn't read the instructions on upgrading correctly. While going from 9.3 to 9.5 went fine, at the next step, it went all the way to 11.3, which has rendered the site unreachable, except for the update.php page.

The problems I'm facing are:

1. It wants the CKEditor module installed, but that's only compatible with Drupal 10
2. I've used Composer to add the MySQL57 module, and added the needed line to my settings.php, but I can't get in to the administrative interface to install the module there.
3. Something somewhere is reporting that the installed Drupal version is below 9.4
4. Attempts to access other site pages produce "Uncaught PHP Exception TypeError: "Drupal\Core\Utility\ThemeRegistry::getPreprocessInvokes(): Return value must be of type array, null returned"" at /core/lib/Drupal/Core/Utility/ThemeRegistry.php line 180

So, my question is:

• Is it possible to rollback to, say, Drupal 10, at this point, or should I just rebuild the site from scratch? (I have access to an ancient backup of the site.)

I should add that there's something weird going on with the installation of Drush I'm working with as it seems to only be interacting with one of the multiple sites we have with this hosting provider, and it's not the problem site.