I’m not sure about Lemmy, but I found this post to be a good explanation of how Pixelfed interacts with Mastodon.
Based on what it says there, I wouldn’t really expect it to play-nice with Lemmy though. We might be able to access Pixelfed posts here on Lemmy, but almost certainly not the other way around - because Pixelfed requires an image in every post.
I’m not sure about Lemmy, but I found this post to be a good explanation of how Pixelfed interacts with Mastodon.
Based on what it says there, I wouldn’t really expect it to play-nice with Lemmy though. We might be able to access Pixelfed posts here on Lemmy, but almost certainly not the other way around - because Pixelfed requires an image in every post.