ContainerAwareEventDispatcher::dispatch(): Argument #1 ($event) must be of type object, string given

For clarification, this syntax change is required for Symfony 4.3+. Drupal core added the deprecation notice in #3055194: [Symfony 5] The signature of the "Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher::dispatch()" method should be updated to "dispatch($event, string $eventName = null)", not doing so is deprecated since Symfony 4.3. → .

This change will be required for D10 compatibility, since Symfony5/6 enforce the new syntax.

Just tried this patch and it does not apply against 5.0.x-dev@dev

Drupal 9 is no longer supported. This version of the module this was opened against only supports Drupal 9. If this is still something you want addressed in the current 5.x version of the module, please update and provide some next steps.