Первая программа на React — React Router v6 — минимум

import { BrowserRouter, Routes, Route, Link, NavLink } from 'react-router-dom';
import Home from './pages/Home';
import About from './pages/About';
import NotFound from './pages/NotFound';

export default function App() {
  return (
    <BrowserRouter>
      <nav>
        <Link to="/">Главная</Link>
        <NavLink to="/about">О проекте</NavLink>
      </nav>
      <Routes>
        <Route path="/" element={<Home />} />
        <Route path="/about" element={<About />} />
        <Route path="/users/:id" element={<UserProfile />} />
        <Route path="*" element={<NotFound />} />
      </Routes>
    </BrowserRouter>
  );
}