If you mean lemmy.world, Lemmy doesn’t display microblog posts unless they’re posted to a community, which is a confusing process. Threads isn’t fully federating right now anyway though. Even if you’re on Mastodon, you’ll only be a able to see posts from specific Threads accounts who have had federation enabled, which is mostly just a few engineers iirc.
If you mean lemmy.world, Lemmy doesn’t display microblog posts unless they’re posted to a community, which is a confusing process. Threads isn’t fully federating right now anyway though. Even if you’re on Mastodon, you’ll only be a able to see posts from specific Threads accounts who have had federation enabled, which is mostly just a few engineers iirc.