Portal sample code of React TypeScript Cheatsheet seems broken

I'm using a pretty strict version of TS and ESLint.

I ripped this portal from the docs here: https://react-typescript-cheatsheet.netlify.app/docs/basic/getting-started/portals/

I modified the code to the below:

import React, { useEffect, useRef, ReactNode } from 'react'
import { createPortal } from 'react-dom'

interface Props {
  children?: ReactNode
  portalId: string
}

export const Portal: React.FC<Props> = ({ children, portalId }) => {
  const el = useRef(document.createElement('div'))

  useEffect(() => {
    const portalRoot = document.querySelector(`#${portalId}`) as HTMLElement

    const current = el.current

    portalRoot.appendChild(current)
    return () => void portalRoot?.removeChild(current) // error thrown here?
  }, [portalId])

  return createPortal(children, el.current)
}

Error below:

Expected 'undefined' and instead saw 'void'

When I remove the void (can't use undefined, otherwise rest of code is unreachable), as such:

import React, { useEffect, useRef, ReactNode } from 'react'
import { createPortal } from 'react-dom'

interface Props {
  children?: ReactNode
  portalId: string
}

export const Portal: React.FC<Props> = ({ children, portalId }) => {
  const el = useRef(document.createElement('div'))

  useEffect(() => {
    const portalRoot = document.querySelector(`#${portalId}`) as HTMLElement

    const current = el.current

    portalRoot.appendChild(current)
    return () => portalRoot?.removeChild(current) // how to fix?
  }, [portalId])

  return createPortal(children, el.current)
}

This results in another error:

Argument of type '() => () => HTMLDivElement' is not assignable to parameter of type 'EffectCallback'.
  Type '() => HTMLDivElement' is not assignable to type 'void | Destructor'.
    Type '() => HTMLDivElement' is not assignable to type 'Destructor'.
      Type 'HTMLDivElement' is not assignable to type 'void | { [UNDEFINED_VOID_ONLY]: never; }'

How to fix?