Hi everyone,
Since Platform Server - 11.8.0 (May 2020), you can use Radio Group Widget in your Reactive Web and Mobile apps. To build and deploy an app with this widget in UI, you also need to update Service Studio to 11.7.2 or above and OutSystems UI to 2.4.0 or above. (Latest stable versions are recommended.)
Here's a quick article on how to use this widget.

As always, thank you for sharing your feedback and ideas. They help us build a better product.