This site is currently struggling to handle the amount of new users. I have already upgraded the server, but it will go down regardless if half of Reddit tries to join.
However Lemmy is federated software, meaning you can interact seamlessly with communities on other instances like beehaw.org or lemmy.one. The documentation explains in more detail how this works. Use the instance list to find one where you can register. Then use the Community Browser to find interesting communities. Paste the community url into the search field to follow it.
You can help other Reddit refugees by inviting them to the same Lemmy instance where you joined. This way we can spread the load across many different servers. And users with similar interests will end up together on the same instances. Others on the same instance can also automatically see posts from all the communities that you follow.
Edit: If you moderate a large subreddit, do not link your users directly to lemmy.ml in your announcements. That way the server will only go down sooner.
For non technical users, the idea of instances can be a very confusing concept (the email analogy is a good one but its still confusing for people). I know you guys have a lot on your plate in terms of development wise, however I hope that prioritizing keeping lemmy.ml up is high up there. I say this because its the instance that most users from Reddit will flock to. And the last thing they need is to create an account then have the site go down for 6 hours. I havent experienced it going down. Although hopefully you have a backup site for when it does (what I mean is just a page that says your down/your working on fixing it… Try these instances instead.)