* Ubuntu 20.10 and 21.04 both seem to toggle (hide) the password as soon as you hit Enter.
* The GUI process (gnome-shell owned by user 'gdm') should vanish as soon as you log in. So it shouldn't remember anything. Maybe then the first problem is your login screen's gnome-shell process is hanging around?
Also worth noting:
* Ubuntu 20.10 and 21.04 both seem to toggle (hide) the password as soon as you hit Enter.
* The GUI process (gnome-shell owned by user 'gdm') should vanish as soon as you log in. So it shouldn't remember anything. Maybe then the first problem is your login screen's gnome-shell process is hanging around?