Redirect Main Home Page url to category URL without plugin

You can use the following code:

add_action( 'request', function( $request ){
    if( empty( $request ) ){
        wp_safe_redirect( get_home_url() . '/lunchtime-results/' );
        exit;
    }
    return $request;
});

This can be added to your theme’s functions.php file.

The code checks the current request arguments. When visiting the home page the request is empty; in all other cases it would include some arguments.

So if the request is empty (is home page) it redirects to a new URL setting the HTTP status to 302(Found).