Workaround:

Press Ctrl+Alt+F2 to enter the terminal.
Log in manually using the original user account and the password.
Use the "startx" command to enter the GUI.
Go to the "User and Accounts" menu to add a new user and make sure the password meets the Plasma password requirements.
Delete the original user account.
Install and enable gdm3 using the "systemctl" command.
Reboot the system.

Expected Results:
The SDDM login screen should allow the user to log in successfully without freezing or showing an "unknown user" error.

Actual Results:
The SDDM login screen freezes after entering the password or freezes on a black screen. The login screen shows an "unknown user" instead of the actual user name that was used on XFCE.

Additional Notes:
After switching to a new user account and deleting the old user account, gdm3 is the only display manager that works, while SDDM and LightDM still freeze on the login screen.