Depending in what learning stage you are (ArcoLinux learning phases), what ISO you are on ArcoLinuxD or Arch Linux or what distribution you are using …
IF you are also using LIGHTDM as your login manager, you may see a “dynamic user” when logging in. See image.
Here is how we can get rid of this dynamic user on the login screen of lightdm.
Go to /etc/lightdm/users.conf and add
to the last line so you get
hidden-shells=/bin/false /urs/bin/nologin /sbin/nologin
Other solutions is to install an extra package
sudo pacman -S accountsservice