You should still be able to configure your descriptor with a HistoryPolicy
in JPA using a DescriptorCustomizer.
To use a historical query you can use the EclipseLink JpaEntityManager
interface to create a JPA Query using a EclipseLink DatabaseQuery
(ReadAllQuery, etc.). For a HistoricalSession you would need to access
the EclipseLink Session from the JpaEntityManager and acquire a
HistoricalSession from this using the native EclipseLink API.
Please log an enhancement request to have JPA support added for historical
sessions.