The metabox appears on all post types by default, and you can use the
searchwp_related_excluded_post_types filter to exclude certain post types.
But rather than listing a bunch of excluded post types, I often prefer listing the few post types to include.
In the code below, I have an
$allowed array listing the post types I want it on. It then generate a list of all other post types and excludes SearchWP Related on those.