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.
Beehaw has a concerning financial post at the top of their frontpage that may indicate they might struggle too when the massive wave of Reddit exodus occurs.
I guess I have to figure out what instances to suggest to people. I do find that direct instance suggestions is the way to go, so I guess I gotta write up a list.
Ideally, some pre-existing communities on Reddit would create their own instances similar to how often they have their own Discords, and have large amounts of users migrate that way. But there's a huge, wide, amount of technical difference between those two things. You can't exactly easily find capable Lemmy admins.