I reported this at the time I upgraded my two systems to F30, and find that it's still true with F31.
On my main (desktop) machine, there are two users, one of which (me) is flagged as the administrative user; the other is a mere mortal. My userid was displayed on the Gnome login screen; the other accessible by clicking the "Not shown" link on the screen.
After the F29->F30 upgrade, the order of the two users was reversed, with the non-admin user displayed by default. My own account is accessible via the "Not shown" link.
This has not changed after my in-place (via dnf) upgrade to F31. The secondary, non-admin user is displayed as the default login on the login screen.
On my other system, a laptop, there was only one user account created prior to the F29-F30 upgrade. When I ran the F29->F30 upgrade and rebooted, I was FORCED to create a (new) admin user account, despite there being one admin user already there. The new user now appears first on the Gnome login screen; the existing user is accessible, again, via the "Not shown" link.
This did not change after my in-place (via dnf) upgrade to F31. The newly-created userid is displayed as the default login on the login screen.
While the extra click on "Not shown" is not a major big deal, I'm unable to figure out how to flip-flop the two userids on the systems so that the primary user appears on the login screen.
Suggestions/discussion welcome. Thanks.