I have setup bskysocial.world to test that (there’s no web interface, just select this domain when logging in or signing up via the app or https://bsky.app)
Note: This is for testing only, I can’t promise it will remain running.
(I am @ruud.bskysocial.world)
It would have been better if they communicated to us first. I don’t disagree that user signups should be spread over instances. We now have a link to https://lemmyverse.net on our signup page so people can check if another instance would fit them better.