Can't generate installer preseed file for bionic

[Jiří Kraml]

Hi All,

I'm trying to generate an installer preseed file for Ubuntu 18.04 as 
described in the documentation [1]. Unfortunately,

$ debconf-get-selections --installer

produces no output. Actually, /var/log/installer/cdebconf is not only 
empty, it doesn't even exist right after the installation. It is only 
created when I install debconf-utils.

The documentation seems to be outdated. To whose attention can I bring this?

And who can tell me how to generate at preseed file?

Regards,
Jiri

P.S. I've already asked this question in ubuntu-users, they suggested I 
ask here