TabViewPageStyleWorkaroundTest.swift

import SwiftUI

enum Tab: String, Identifiable, Hashable, CaseIterable {
    case green, yellow, red
    
    var id: String { rawValue }
}

struct ContentView: View {
    // This needs to be set to the first tab.
    @State var selectedTab: Tab = .green
    
    // This can be set to another tab that you actually want to be set initially
    @State var initiallySelectedTab: Tab? = .red
    
    var body: some View {
        NavigationStack {
            TabView(selection: $selectedTab) {
                Color.green.opacity(0.5)
                    .tag(Tab.green)
                Color.yellow.opacity(0.5)
                    .tag(Tab.yellow)
                Color.red.opacity(0.5)
                    .tag(Tab.red)
            }
            .tabViewStyle(.page(indexDisplayMode: .never))
            .navigationTitle("Test")
            .toolbar {
                ToolbarItem {
                    Picker(selection: $selectedTab) {
                        ForEach(Tab.allCases) { element in
                            Text(element.rawValue)
                                .tag(element)
                        }
                    } label: {
                        Text(selectedTab.rawValue)
                    }
                    .pickerStyle(.menu)
                }
            }
            .onAppear {
                if let initiallySelectedTab {
                    self.initiallySelectedTab = nil
                    // Delay is needed to prevent SwiftUI bug where tapping the first tab wouldn't
                    // change views. This way every view will be loaded.
                    DispatchQueue.main.async {
                        self.selectedTab = initiallySelectedTab
                    }
                }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}