[Plugin: Yet Another Related Posts] Create related BBpress topics in my post

What you want to do is to add a new yarpp_related() call, which will create another set of related links, rather than doing anything within your custom template.

I’m not sure what custom post type you need to refer to for bbpress topics, but you’ll want to refer to that post type in a yarpp_related() call. Info on the yarpp_related() function is here:

https://www.ads-software.com/extend/plugins/yet-another-related-posts-plugin/other_notes/