How to present an alert in visionOS immersive space?

My visionOS app uses an immersive view. If the app encounters an error, I want to present an alert.
I tried in a demo app to present such an alert, but it is not shown. Nearly the same code on iOS presents an alert window.
Here is my demo code, based on Apple's Immersive Environment App template:

import SwiftUI
import RealityKit
import RealityKitContent

struct ErrorInfo: LocalizedError, Equatable {
    var errorDescription: String?
    var failureReason: String?
}

struct ImmersiveView: View {
    @State private var presentAlert = false
    
    let error = ErrorInfo(
        errorDescription: "My error",
        failureReason: "No reason"
    )
    
    var body: some View {
        RealityView { content, attachments  in
            let mesh = MeshResource.generateBox(width: 1.0, height: 0.05, depth: 1.0)
            var material = UnlitMaterial()
            material.color.tint = .red
            let boardEntity = ModelEntity(mesh: mesh, materials: [material])
            boardEntity.transform.translation = [0, 0, -3]
            content.add(boardEntity)
        }
        update: { content, attachments in
            // …
        }
        attachments: {
            // …
        }
        .onAppear {
            presentAlert = true
        }
        .alert(
            isPresented: $presentAlert,
            error: error,
            actions: { error in
            }, message: { error in
                Text(error.failureReason!)
            })
    }
}

Since I cannot see any alert, is something wrong with my code? How should an alert be presented in immersive space?