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.
Because you want to rely on someone else's instance. The idiomatic solution would be for a community to host their own lemmy/activitypub instance and join the federation. Then the community has control over their own data. In every sense. If they want to delete something (for breaching law, protocol, or whatever), they are free to do so and don't have to ask anyone else.
Please no. I mean there is IPFS out there that somewhat works like that, but I don't really like that. First, the ever-growing amount of data means that every instance has to keep up with it. If they wouldn't replicate it, the deletion of a single instance would still eliminate the data, even if there were references in a block-chain.
Also: the ability to "forget" is important. Not everything needs to live on forever. That it currently does, can already be a big problem. Look how peoples lives got almost ruined because someone dug up tweets from 10 years ago that were stupid. Solving the issue of data ownership is IMO one of the bigger things we need to keep in mind when designing a better web. Federation with the ability to "just" bring your own instance along where you are the owner is one of these options.