Hello. I’m possibly still confused. I looked at the provided link in your original post and tested an installation of UCS from scratch in a virtual machine before commenting. Instructions for the Step1 are pretty clear. In the Step 2, “Ctrl-Alt-F2” did not work in my setup because of the existing key reservations, so I ended up using tty4 and needed to login.
If one does the base installation, which is basically a graphical Debian server installation, the root password is known as it is to be entered by hand during that time.
Otherwise, the unknown root password issue could be resolved by reinstalling UCS or chrooting into UCS after booting from a live Debian ISO and resetting the root password.
I cannot easily test the same on a physical box to verify if “Ctrl-Alt-F2” would open something different other than the login prompt you and I were seeing. Also, I wonder what setup the author of the tutorial was using, under which the switch to the passwordless BusyBox console is expected. Another difference may be that I tested UCSv5 while the tutorial is for UCSv4. They gotta be somewhat different under the hood. Regardless, if the root password is known, any secure tty should not be a show stopper.