Switch off unique nicknames

Force a unique nicename. This forces the user to choose a Nickname that is different from the login name which will be used for the author slug and other appropriate areas.

Is there anyway to switch off the above feature?

Due to strict GDPR rules when creating a user the client has asked we don’t enter first name and username. There is no way to enter a nickname when creating a user and I keep getting an error message asking me to enter a nickname or first name and surname. I’d lie to switch off the above feature in the free version of the plugin.