React hook useRef not working with styled-components and typescript

I've finally found a solution:

const inputRef = useRef() as React.MutableRefObject<HTMLInputElement>;

---

It works for me:

import React, { useRef, useEffect } from 'react';
import styled from 'styled-components';

const StyledInput = styled.input`
  background: transparent;
`

const MyForm = () => {
  const inputRef = useRef() as React.MutableRefObject<HTMLInputElement>;

  useEffect(() => {
    if (inputRef && inputRef.current) {
      inputRef.current.focus();
    }
  }, []);

  return (
    <StyledInput ref={inputRef}/>
  );
}

As an alternative to the current accepted answer, you can also do:

const inputRef = useRef<HTMLInputElement>(null);