I am using the related posts plugin with a number of custom posts and taxonomies. It look like by default related posts are only selected from the same custom post type. I have added a filter that includes all cpts as "post_type", but that doesn't change anything... Is there a way to extend the selection of related posts across other cpt?
Welcome to our forum.
By default, it will query from same post type and same category or custom taxonomies that exist on current post, that make it related posts query, although you can override post query arguments by filter hook, please see the documentation
Please let me know if you need any help.