administrator – Setting a default username in Admin authentication dialogs?

For years, whenever I was presented with a dialog asking for Administrator authentication, the Username field was already filled in. I only needed to fill in the password.

This changed (I think) recently when I got an Apple Watch and the “unlock with Apple Watch” setting in the Security & Privacy system prefs pane got enabled. I disabled that setting, but still, since then, the Username field comes up empty and I have to fill it in every time.

Any idea of how can I go back to having a default Admin Username filled in automatically?

Some further detail and things I have tried:

  • I’m in macOS Big Sur 11.4, but as stated, the default Admin username had been there across OS versions for as long as I can remember.
  • I’m in a non-Admin account, obviously. There is only 1 Admin account in the machine, also owned by me, rarely used.
  • I tried logging in as the Admin account. In there, the authentication dialogs do fill in the Admin’s name by default.
  • I have tried turning on and off Fast User switch, the showing of names in the log in screen, have recreated the TouchID fingerprints of the Admin account, and logged that account into its AppleID account. Nothing helped.