There is a delay state variable controlled by a slider, but its value is not used.
Pass the delay value to your custom useCounter Hook, and change the useCounter Hook to use the passed delay instead of hardcoding 1000 ms.
Here is the code:

//App.js
import { useState } from 'react';
import { useCounter } from './useCounter.js';
export default function Counter() {
  const [delay, setDelay] = useState(1000);
  const count = useCounter();
  return (
    <>
      <label>
        Tick duration: {delay} ms
        <br />
        <input
          type="range"
          value={delay}
          min="10"
          max="2000"
          onChange={e => setDelay(Number(e.target.value))}
        />
      </label>
      <hr />
      <h1>Ticks: {count}</h1>
    </>
  );
}

//useCounter.js
import { useState, useEffect } from 'react';
export function useCounter(delay) {
  const [count, setCount] = useState(0);
  useEffect(() => {
    const id = setInterval(() => {
      setCount(c => c + 1);
    }, delay);
    return () => clearInterval(id);
  }, [delay]);
  return count;
}

I’ve been trying to make the useCounter hook respect the delay set by the user in the Counter component, but it doesn’t work.