You have requested a non-existent service "serializer.normalizer.content_entity.jsonapi"

I am quoting my comment from ✨ Support entities that are neither content nor config entities Needs work :

@thursday_bw I have also experienced the issue that you have mentioned in #59 but only on Drupal 9.4.x. This is a pretty weird one. I did some debugging and I believe this line causes that problem because if I change (correct?) that line to $original = $container->getDefinition($service_id); then the issue disappears. Also, the good new is that this code was removed and deprecated and removed since Drupal 9.5.0, see https://github.com/drupal/core/blob/10.0.3/lib/Drupal/Core/DependencyInj... and #2531564: Fix leaky and brittle container serialization solution → .

Update, update, the Core patch could have caused this issue: https://www.drupal.org/project/drupal/issues/3042467#comment-14940083 ✨ Support entities that are neither content nor config entities Needs work

But when that core patch finally lands, the change in #2 becomes necessary.