Create an user with empty password
sudo useradd test-user-0
echo test-user-0:U6aMy0wojraho | sudo chpasswd -e
The password prompt still shows unfortunately.
But if you just hit enter without typing anything, and it logins as the user
-e flags tells
chpasswd that the password is already encrypted, and
U6aMy0wojraho is the hash of the empty string.
Tested on Ubuntu 18.04.
Terminal autologin with
On the terminal at least, you don't need to create an user without a password to allow someone to not type their passwords every time.
I was able to do this on BusyBox by modifying
inittab: How to login automatically without typing the root username or password in Buildroot BusyBox init?
So I believe that it should not be very hard to adapt that technique by modifying Ubuntu 18.04's systemd init system scripts to setup a
getty -a <user> terminal as mentioned in that answer, although I haven't tried to do it myself.