fieldcollection
There are 2 repositories under fieldcollection topic.
erpushpinderrana/migrate_missing_content_translations
Drupal 7 to Drupal 9 - Migrate only missing content translations
backdrop-contrib/field_collection
Field Collection provides a field for entities (nodes, users, taxonomies, comments, etc.) to which a collection or group of any number of fields can be included and treated as a whole or single unit.