Loops is a federated alternative to TikTok created by Pixelfed. Once it first came out, users were able to sign up for early access. Confirmation emails weren't sent right away, but today they announced that emails were being sent out, and registration is now closed.
I got a confirmation email today, attached in the image. I will be loosely documenting my experience, and may (no promises) make a writeup about it.
Got an invite, too. But without an app there is nothing you can do, just change password and write a bio.