Not that I know of, but here are some between Lemmy and Mastodon:

• Upvotes in Lemmy don’t translate to favorites in Mastodon
• From the Mastodon side communities are normal accounts that boost published posts.
• From Mastodon Lemmy’s posts are top-level messages (i.e. not a response), and comments are responses to the original message.
• You can post to a Lemmy community from Mastodon by publishing a post and tagging the community (@[email protected])