You could create your custom "fetching hook" and there you can fetch the data and set the loading state:

const { useEffect, useState } = React

const useFetchUsers = () => {
  const [users, setUsers] = useState([])
  const [loading, setLoading] = useState(false)
  
  useEffect(() => {
    setLoading(() => true)
    // setTimeout added to emphasize async nature
    setTimeout(() => {
      fetch('https://jsonplaceholder.typicode.com/users/')
        .then(response => response.json())
        .then(json => setUsers(() => json))
        .finally(setLoading(() => false))
    }, 1000)
    
  }, [])
  
  return {
    users,
    loading,
  }
}

const UserItem = ({ id, name, username, email }) => {
  return (
    <div>
      {name} - {username} - {email}
    </div>
  )
}

const App = () => {
  const { users, loading } = useFetchUsers()
  
  return (
    <div>
      {
        !loading
        ? users.map((user) => {
          return (
            <UserItem
              key={user.id}
              {...user}
            />
          )
        })
        : "Loading users..."
      }
    </div>
  )
}

ReactDOM.render(
  <App />,
  document.getElementById('root')
);

<script crossorigin src="https://unpkg.com/react@17/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@17/umd/react-dom.development.js"></script>
<div id="root"></div>

Ok so this was not as trivial as I thought (at least for me), huge thanks to @Bergi and to @muka.gergely and the authors of this resource that helped me get the final solution: https://www.debuggr.io/react-update-unmounted-component/

This is what I came with:

export const LayoutValidator=({children})=>{
  const {invalid, auth} = useFetchToken()
  return !invalid ? <Intermediate children={children}/> : <Navigate to="/" />
}

function Intermediate ({children}) {
  const {invalid, auth} = useFetchToken()
  return !auth ? <SplashScreen/> : children
}

function useFetchToken() {

  const { token } = JSON.parse(localStorage.getItem("loggedUser") || '{}')
  const [invalid, setInvalid] = useState(false)
  const [auth, setAuth] = useState(false)

  useEffect(()=>{
    let mounted = true
    setInvalid(() => true)
    fetch(`${urlValue}/api/validate-token`, {
    method: "POST",
    headers: {
      authorization: token,
    }
  })
    .then(ans => ans.json())
    .then(ans => mounted && setAuth(()=>ans.auth))
    .catch(err => console.log(err))
    .finally(setInvalid(()=>false))

    return () => mounted = false;
  },[])
  return {invalid, auth}
}

In my situation, it worked perfectly, hope this helps someone in the future.