How does Lemmy intregrate with the rest of the Fediverse? - eviltoast

So I’ve been trying to get myself accustomed to this place and understand whats going on.

To my understanding: -There are Lemmy instances -Instances communicate with each other to create the “Lemmyverse” -There a larger version of this that encapsulates all (or a lot of) services that use ActivityPub called the “Fediverse”

My question is how or if would I interact with said other services from Lemmy? Is that possible? Could I say, see Mastodon or Peertube content from Lemmy? If I can, how? Do I sign up to those sevices with my existing Lemmy account? Can or will I soon be able to interact with everything through one account? Because that seems to me like it should be possible assuming everything and everyone is federated.

How is Lemmy interconnected with the Fediverse right now, and how might it become further connected in the future?