Okay, can you please clarify one thing for me… you used the theme I’m using, made a bilingual test site, and Related posts are working for both languages – and you didn’t use Polylang. Is that right? If that’s the case, I don’t need the plugin at all. I already have TranslatePress installed for custom translations, and I do the rest manually anyway. If it’s going to mess up with the settings, I really wouldn’t want to keep it.
Thoughts?