Cannot log into freshy installed Ubuntu Server 16.04.3: login incorrect?

I installed Ubuntu Server 16.04.3 (kernel version 4.4.0.87) in a VirtualBox Virtual Machine. No fancy settings, pretty much just a straightforward default install.

After the installation was finished and I booted the first time, I was unable to login ("login incorrect").

After some attempts in disbelief, I assumed I must have made a typing mistake during the installation, so I just installed the whole thing again. Same problem. I was now convinced something was fishy, so I reinstalled it again, took extra care and triple-checked every step, making 100% absolutely certain I am entering the right username and password everywhere.

During this last installation I made screenshots of the installation process. Click on each image for the full resolution version:

1. Specifying the username:

   
   ^{(Click images to enlarge)}

2. Specifying the password:

3. Confirming password:

4. After installation was finished, booting my freshly installed Ubuntu:

I am absolutely 100% sure I am entering the exact right details. No dumb mistakes like keeping caps lock on or mistakenly using a Dvorak keyboard or anything.

What am I doing wrong?

(edit) I also tried the 'recover lost password' procedure. Note that this doesn't really apply here, I didn't lose my password, I'm 100% sure, see screenshots from installation. Nonetheless I tried this anyway, going in rescue mode and root prompt, and when I do: passwd kenneth
To my surprise I get: passwd: user 'kenneth' does not exist

Again, note that I'm 100% sure that I specified my username kenneth during the installation.

Then I did: more /etc/shadow and I get a list of typical system user accounts, like root, daemon, bin, sys, and so on. But no 'kenneth' account nor any other that looks like a user account, only the typical system accounts. In fact there are none with an actual password, they all have ! or * for the password hash.

I also did ls -al /home, nothing there.

What could be the reason for an Ubuntu installer to not create the user account as specified during the installation?

Note that I didn't get any errors during the entire installation, everything worked smoothly and straightforward from beginning till end.