Lemmy has no way to follow a person, so it's impossible. Not sure where such thing sits on a roadmap or whatever, but I get the impression it isn't a priority, at all maybe.

Lemmy does federate decently with mastodon though, as you point out, so consuming lemmy content from mastodon can work, but isn't great. Following a community for instance provides all posts and comments, which quickly becomes a firehose. I imagine most don't do that for long.

~~Following lemmy accounts on the other hand, IME, works nicely, as only posts are federated over, which is a much more manageable feed.~~ EDIT: Sorry, this was wrong, comments as well as posts from a specific user do get federated across.

And replies all work well too, so once you've made contact with a thread on mastodon by replying, it will all behave naturally for the mastodon platform, which is quite nice to see actually.

There's also kbin, which tries to fuse the two platforms, but even there, you can't look at a feed of just the people you follow.