I think you can, by doing @piefed_meta@piefed.social

It's almost the same as on Lemmy/PF except here we use ! on the front.

You can mention a Piefed/Lemmy/etc. community in your Mastodon post, and it will show up in that community.

For example, here's something I originally posted on Mastodon, but made it show up in !mechanicalkeyboards@lemmy.ml by mentioning that community in my post: https://lemmy.ml/post/32525858

However, I heard that Lemmy ignores it if you mention multiple communities in the same post, probably to prevent spam. Not sure if Piefed does the same thing. I'm not sure how to get the same Mastodon post to show up in multiple communities. Maybe it just works if you mention multiple communities -- I haven't actually tried it.

Also, I don't think there's a way to make someone else's Mastodon post show up in a community, which is probably a good thing (to avoid unwanted attention). Aside from just creating a post in that community that just has a link to the Mastodon post, of course.