Since while I was doing research I stumbled accross this thread, but it didn't bring me to the result I wanted. So I decided to register here to point out my approach to aquire the need of fetching posts with multiple post types.

1st) I registered a new RestAPI Endpoint to get the ability to query multiple post types:

//PHP
add_action( 'rest_post_query', function( $args, $request ){
    $post_types = $request->get_param( 'type' );
    if( ! empty( $post_types ) ){
        if( is_string( $post_types ) ){
            // filtering posttypes, seperated with comma into an array, ignoring square brackets
            $post_types = explode( ',', str_replace( array( '[', ']') , '', $post_types ) );
            foreach ( $post_types as $key => $post_type ){
                $object =  get_post_type_object( $post_type );
                if( ! $object || ! $object->show_in_rest   ){
                    unset( $post_types[ $key ] );
                }
            }
        }
        $args[ 'post_type' ] = $post_types;
    } else {
        // fallback: no type defined, return post as default
        $args[ 'post_type' ] = 'post';
    }
    return $args;
}, 10, 2 );

Check your new API endpoint easily by calling it with your browser

https://*yoururl.com*/wp-json/wp/v2/posts?per_page=10&categories=0&type=posts,page

I don't use the Gutenberg function getEntityRecords anymore to fetch posts. I choose that way performance wise to avoid multiple calls of getEntityRecords.

2nd) In my Gutenberg block I created a hook to call:

export default function useFetchPosts( url ) {
    const [data, setData] = useState( null );
    useEffect(() => {
        async function loadData() {
            const response = await fetch( url );
            if(! response.ok ) {
                return false;
            }
            const posts = await response.json();
            setData(posts);
        }
        loadData();
    }, [url]);
    return data;
}

3rd) to get the posts I just call it like this inside my edit block:

// parsedCategories and
// parsedPostTypes  have to set and parsed by you before ofcourse ;)
const numberposts = 10;
const postFields = '&_fields=id,author,link,title,_links';
const posts = useFetchPosts( 'https://'+window.location.host+'/wp-json/wp/v2/posts?per_page='+numberposts+'&categories='+parsedCategories+'&_embed=author&type='+parsedPostTypes+'&orderby=date&order=desc'+postFields );

Check out the restAPI reference for available args and parms: https://developer.wordpress.org/rest-api/using-the-rest-api/global-parameters/

Cheers