Most people use password or fingerprint for authentication on their Apple computers, but there are cases when you need to enter the user name for logon.
For example, the computer on macOS can be used by multiple people under different accounts, and there are times when users forget their usernames.
To change the display settings entering the system should:
If you go to the system fails, then there is also another option:
This way you can also reset the password on a system that was not encrypted with the FileVault.