So there’s a couple of thoughts here, and I’ve only experimented a little bit.

You can post directly from your Mastodon account to a community by calling out the community by its address like @fediverse@lemmy.world in your post (toot) (don’t think anything will happen by me using it here). You’ll see the Mastodon post as a community style post in the community like this: https://lemmy.world/post/1222638

You can my click my mas.to profile and see some things in the Lemmy context - not my verified links, but things like my profile picture and background, bio, Cake day, sending me a message.

I don’t know how to interact with Mastodon users viaa Lemmy or Kbin. Like above if I reference my Mastodon user @hemmes@mas.to I don’t believe anything happens.

So OP’s only options are posting a snapshot or, my choice, he can add the Mastodon post link to his Lemmy community post (in the header not the body) and have the same results as any other web link - the Mastodon media would get a thumbnail in the community post listing, with maybe some relevant content preview, etc. While that will deliver a superior viewing experience, that’s not actually communicating with ActivityPub through the Fediverse, it’s simply a web link to the Mastodon instance server’s user’s post.

Edit: Okay, so it looks like mentioning my mas.to handle does indeed alert me (almost instantly in this case), that’s cool!