InvalidArgumentException: The entity cannot be translated since it is language neutral (und). in Drupal\Core\Entity\ContentEntityBase->addTranslation()

Seems like a duplicate of https://www.drupal.org/project/paragraphs/issues/3082703 🐛 Paragraph translation source language is not set when parent is under Content Moderation Needs work .

In case someone is experiencing the same exception (InvalidArgumentException: The entity cannot be translated since it is language neutral (und)), but does not have the content_moderation module enabled, it's probably due to this other scenario: https://www.drupal.org/project/paragraphs/issues/3378070 🐛 Source language is not set in nested Paragraphs when transitioning from a locked language (und, zxx) to another language. InvalidArgumentException: The entity cannot be translated since it is language neutral (und). Active .

I think this was fixed by 🐛 Error editing content with undefined language, add check Fixed