Hi there,
there are tonnes of them on the wordpress.org
https://wordpress.org/plugins/search/related+posts/
The thing to be mindful of is true related posts such as what YARP or Contextual Relate Posts these all require a fairly hefty algorithm to make the relationships. So they can have a hit on performance.
Whereas there are other less server hungry plugins that create relationships only by taxonomy term such as this one:
https://wordpress.org/plugins/same-category-posts/
Theres a lot of options out there.