first_boot: Stuck out of plinth if accessed before setup completed

When starting a fresh FreedomBox image, if I try to access Plinth before background setup process is completed, I get the note to wait until it is completed. If I click some of the links that are shown (Log In or FreedomBox logo), after the setup process is completed, I get in a "stuck" state. I'm given a login form, but have not yet created a user. I don't see a way to get to the normal user creation form.