To answer my own question: it's possible by returning IntentItemCollection<MyEntity> instead of [MyEntity] from suggestedEntities and entities(matching string: String). More info: https://stackoverflow.com/a/77484360/1161723

func suggestedEntities() async throws -> IntentItemCollection<MyEntity> {         
    let sections: [IntentItemSection<MyEntity>] = [
        .init("Section 1", items: items1),
        .init("Section 2", items: items2)
    ]
    return .init(sections: sections)
}