Lemmy doesn't offer native account migration, but LASIM is a standalone tool to migrate many settings.
It doesn't redirect anyone to your new account, you'll still need to leave a goodbye post or message in your profile pointing to your new account if you want people to find you. And it won't migrate your post/comment/vote history (which I don't think is possible for any tool to do right now). But it will migrate your subscribed community list and a variety of other settings so your new account feels homey to you at least.
And many people have done this with no tool. It's not THAT much work to copy settings over by hand.