I can't think of a way to use EF Core and DB Change Notification directly together easily. EF Core uses generic ADO.NET APIs. It can't access ODP.NET-specific APIs. DB Change Notification is specific to ODP.NET.
You could execute a query with EF Core. Then, capture the SQL executed and re-execute it with ODP.NET so that it can be registered with DB Change Notification. You don't need to actually retrieve the results in the re-execution. When a change occurs, the event handler will have EF Core query again to retrieve the new data..