We may want to allow users to skip the definition of the backend type, or even of the backend, when there is only one registered backend factory alias?
See in particular org.hibernate.search.v6poc.engine.impl.IndexManagerBuildingStateHolder#startBuilding and org.hibernate.search.v6poc.engine.impl.IndexManagerBuildingStateHolder#createBackend: when the backend name is missing we should use "default", and when the default backend type is missing we should use that single registered backend factory alias.
Moving to 6.1: we don't want this in 6.0, because this could allow users to boot Hibernate Search even though they didn't migrate their configuration at all.
Actually we'll use another approach to detect obsolete Hibernate Search 5 configuration in Hibernate Search 6. Moving this ticket back to 6.0.