Don't think so, also not sure how Mastodon feeds work with Lemmy as they aren't really upvoted/downvoted on. Though the opposite works where you can follow communities/accounts from Mastodon.
For me mastadon didn't 'stick' but I was never a big twitter user. So I failed to jump from from the big social networks to mastadon because the experience was weird. I guess you can follow lemmy communties but I had no idea how to find them and it mostly looked like following other people like on twitter.
Whereas the UI and everything on lemmy is much more like what Im used to it (reddit) - so it 'stuck' for me.
I still have the mastadon account collecting dust and might go back over there now that I understand more, but as I prefer to follow subjects over people I dont feel like Im missing out
Pretty different experience, but if you prefer it that way you can. You can actually follow specific communities from Mastodon, but it's not nearly as good of an experience. I just install both apps and have separate accounts for both.
Posting to lemmy through mastodon is a thing (hello there!), but yeah, I don’t think you can follow a mastodon account through lemmy unfortunately.
EDIT: I lied! Found the server admin I think at this link: https://lemmy.ml/u/beheerder@social.overheid.nl but I think they need to specifically post to a lemmy server in order to have posts show.