There are many ways to develop cross-platform apps, and one framework Microsoft actively supports is React Native.
In fact, Microsoft maintains its own variant of the framework with React Native for Windows (or React Native UWP), which has been optimized for the special requirements of Windows 10 and with a special focus on performance. The new Xbox app is for example coded in React Native and benefits from the improved performance compared to the older Electron version.
Microsoft has now released the React Native Gallery app in the Microsoft Store. The React Native Gallery is a React Native Windows application which displays the range of React Native components with Windows support and gives developers insight into the framework.
The app is in principle very similar to the WinUI 3 Controls Gallery app which Microsoft released to the Store a few weeks ago.
Find the app in the Store here.