Selectors for React context API?

You fundamentally misunderstand Context. Context is not a state management solution, it is a storage solution. It has no opinion about any processes for managing state. If you want to use the selector pattern you’ll need to write it yourself.

To elaborate, people often compare Context to local state, Redux, MobX, etc. The real comparison is Context + Custom Solution vs Redux, MobX, etc. Under the hood libraries like Redux use Context. Your solutions for storing state in React are hooks or Context. Both come with an API for getting data in and out. Any enhancements on top of that you have to create yourself. These external libraries provide these enhancements.