On the GNOME login screen you can press [Enter] or [Space], or click (on the latest GNOME, 3.34) or swipe up (on the previous versions) to get to the password entry box, or you can just start typing your password. It's extremely easy and discoverable (because there are so many options, nearly anything you do will take you to the password box). I really don't think there's an issue with it.
This is with stock GNOME (on Arch); I think Ubuntu may ship a skinned / modified / older version of it (which can create UI problems).
So what you're saying is that there's no way to discover it by visual inspection alone; and so my elderly family members could never discover it for fear of breaking something by pressing the wrong button. That's bad UI.
This is with stock GNOME (on Arch); I think Ubuntu may ship a skinned / modified / older version of it (which can create UI problems).