I just found the contrary. In a lemmy search field querying this thread (https://slrpnk.net/post/2450620) comes up empty every time (#Lemmy → Lemmy). Just to get here to respond, I had to search for the support community then browse for this thread. All in Lemmy.

Kbin cannot cross-post to anywhere.. not to another kbin or to lemmy. But I was able to search for a specific #Kbin thread in the lemmy search form, then search for another kbin magazine in lemmy, then use Lemmy to cross-post a kbin thread to another kbin instance.