I don't know much about Xamarin but I know about PyQt and React Native.
However, I don't recommend PyQt because the apps made using PyQt are not that suitable for mobile apps. If you take a look at the PyQt interface, you will be able to see that the features are more of a desktop apps kind.
React Native uses JavaScript. React Native is immensely flexible in upgrading your apps because it allows you to formulate your app code into independent blocks.
In Xamarin, you have to write the code in .NET . The best thing about Xamarin is, that it extends the.NET developer platform with tools and libraries specifically for building apps for Android, iOS, tvOS, watchOS, macOS, and Windows
While the best choice for you depends on various factors but React Native app development is a promising overall choice. In today’s scenario, React Native has steady growth, flawless code structure, and brilliant and large community support. We suggest you go for React Native for your next project owing to its outstanding support from developers, easy availability, and cost-effectiveness.