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.
I feel like for decentralized identity maybe a page could be taken out of Blockchain. Ethereum ledger is duplicated in its entirety on every host, and there are L2s that help spread the load but roll up to the L1. If identity could be attached to something like that, each person has a key to identify themselves. Identity I think would be best separated from all content related to the identity, the user could choose a server to host that data, as well as back it up with like a shared user data backup agreement between a few servers in case one dies. It'd be very similar to raid but the data only needs to be on 2-3 servers. I suppose community data could be the same. I can envision when a new server joins the federation, it could be auto assigned to share with 2-3 similarly sized communities with algorithms making sure there aren't any closed groups of sharing (a->b&c, b->a&c, c->a&b) wouldn't ever want that. They all seems to be the most reasonable solution in my head.