Hide option select item in woocommerce product type

You can filter product_type_selector

add_filter( 'product_type_selector', 'remove_product_types' );

function remove_product_types( $types ){
    unset( $types['grouped'] );
    unset( $types['external'] );

    return $types;
}

Try this. This code should work and it work best with woocommerce 3.4.4 and above. Refrence: https://gist.github.com/tanmay27vats/89f9d67db78c33a6ffa1d844235a5db1

add_filter( 'product_type_selector', 'remove_product_types' );

function remove_product_types( $types ){
    unset( $types['grouped'] );
    unset( $types['external'] );
    unset( $types['variable'] );

    return $types;
}