May be a stupid question.
import {ReactDOM} from 'react-dom/client'; // or import {ReactDOM as ReactDOM} are BAD
...
const root = ReactDOM.createRoot(document.getElementById("root"));
received error:
export 'ReactDOM' (imported as 'ReactDOM') was not found in 'react-dom/client' (possible exports: createRoot, hydrateRoot)
OK only import ReactDOM from 'react-dom/client';
This is different from this post