Как отключить отображение системных пользователей на экране входа в систему (LightDM)

If your system uses AccountsService, you can not hide a user from the greeter screen by reconfiguring lightdm because it defers to AccountsService. That is stated very clearly in the comments in /etc/lightdm/users.conf.

What you need to do instead is to reconfigure AccountsService.

To hide a user named XXX, create a file named

containing two lines:

If the file already exists, make sure you append the SystemAccount=true line to the [User] section.

Via https://askubuntu.com/a/575390