I have read all of the conversation on this topic, and I have tried the solutions suggested to no avail. My duplicate user name appeared on the login screen after updating to Win 10 Version 1909. One thing I tried out of curiosity was to create a new user and password. When I did this, the login screen showed the new user name twice as well. I have since removed that user name, and the two new names were both removed. Any suggestions you might offer would be appreciated.