We have a client coming from WordPress who have been using a plugin called Yoast SEO https://yoast.com/wordpress/plugins/seo/ that they are very happy with. I've never used it, but it seems to provide both simple SEO checks/functions and SEO assistance.
*What SEO packages are people using for Umbraco 13? *
I've never used one myself, but I've seen SEO Checker and SEO Toolkit mentioned here. Both "technical SEO hygiene factors" and "proactive SEO assistance" are what the client is looking for.