I created a list layout to go along with my grid layout, and the list looks just fine in the SwiftUI preview but when I toggle from grid to list it just shows a blank screen. :(

Here's my ContentView

import SwiftUI    

struct ContentView: View {

    let astronauts: [String: Astronaut] = Bundle.main.decode("astronauts.json")
    let missions: [Mission] = Bundle.main.decode("missions.json")

    @State var showingGrid = false

    var body: some View {
        NavigationView {
            ScrollView{
                Group {
                    if showingGrid {
                        GridLayout(astronauts: astronauts, missions: missions)
                    } else {
                        ListLayout(astronauts: astronauts, missions: missions)
                    }
                }
                .toolbar{
                    ToolbarItem() {
                        Button("Switch Layout") {
                            showingGrid.toggle()
                        }
                    }
                }
                .padding([.horizontal, .bottom])
            }
            .navigationTitle("Moonshot")
            .background(.darkBackground)
            .preferredColorScheme(.dark)

        }
    }
}

#Preview {
    ContentView()
}

And here's my ListLayout

import SwiftUI

struct ListLayout: View {

    let astronauts: [String: Astronaut]
    let missions: [Mission]

    var body: some View {
        List{
            ForEach(missions) { mission in
                NavigationLink {
                    MissionView(mission: mission, astronauts: astronauts)
                } label: {
                    HStack {
                        Image(mission.image)
                            .resizable()
                            .scaledToFit()
                            .frame(width: 100, height: 100)
                            .padding()

                        VStack {
                            Text(mission.displayName)
                                .font(.headline)
                                .foregroundColor(.white)
                            Text(mission.formattedLaunchDate)
                                .font(.caption)
                                .foregroundColor(.white.opacity(0.5))
                        }
                        .padding(.vertical)
                        .frame(maxWidth: .infinity)
                        .background(.lightBackground)
                    }
                    .clipShape(RoundedRectangle(cornerRadius: 10))
                    .overlay(RoundedRectangle(cornerRadius: 10)
                            .stroke(.lightBackground)
                             )
                }
            }
        }
    }
}

struct ListLayout_Preview: PreviewProvider {
    static let astronauts: [String: Astronaut] = Bundle.main.decode("astronauts.json")
    static let missions: [Mission] = Bundle.main.decode("missions.json")
    static var previews: some View {
        ListLayout(astronauts: astronauts, missions: missions)
            .preferredColorScheme(.dark)
    }
}

Thanks!

My mistake here was keeping the ScrollView in ContentView. I moved that over to GridView and it worked!