Go to the “Users” module.
Open the “Users and Groups” page.
Press 🔎 to search for the user name.
Press “Edit”
Edit the “Username”.
Press “Update”
After changing the user name, you must add it to the “External access” permission
Go to the “Users” module.
Open the “Users and Groups” page.
Select ⭕ next to “Exception users”
Press “Load”
Choose the “Username” from DDL.
Press “➕”
Press “Save”