Statistics show guest on

Ideally as a widget

While Jetpack doesn’t include a widget that does that for you, you can use the WordPress.com Stats REST API endpoint to build your own stats function:
https://developer.wordpress.com/docs/api/1.1/get/sites/%24site/stats/

You could also use the old Stats API, as explained in this tutorial:
https://webdesignerhut.com/display-post-views-in-wordpress/