React RXJS Subject State https://playcode.io/1088821

App.jsx

import React from 'react';
import { BehaviorSubject } from 'rxjs';
import { useObservable } from 'react-use';

const subject = new BehaviorSubject(1);

const useSubjectState = (subject) => [useObservable(subject), (value) => subject.next(value)]

const Increment = () => {
  const [state, setState] = useSubjectState(subject);

  return <div><button onClick={() => setState(state + 1)}>increment</button><p>{state}</p></div>
}

export const App = (props) => {
  return (
    <div className='App'>
      <Increment />
      <Increment />
    </div>
  );
}