By default, the contents of which directory will be copied to a new user's home...

The /etc/skel directory contains files and directories that are used as a template for creating a new user’s home directory. The useradd command uses the -m (or --create-home) option to create the user home directory as /home/username and copy the files from /etc/skel to it. The files in /etc/skel are typically initialization files such as .bashrc, .profile, and .bash_logout that set the user’s environment variables, aliases, and other preferences. The system administrator can customize the /etc/skel directory to provide a consistent and convenient initial setup for new users. References: 

https://www.howtouselinux.com/post/create-new-user-with-home-directory-in-linux

https://linuxize.com/post/how-to-create-users-in-linux-using-the-useradd-command/