Problem
The NetBIOS name is created automatically based on the domainname in the installer. It is not possible to edit it. There are scenarios where you need to define the NetBIOS name anyway - maybe because you want to takeover a Windows AD environment where NetBIOS name is different from the DNS/Kerberos domain name, or because the limit of 15 characters for the NetBIOS domain name leeds to an ugly abbreviation (e.g. future-inc-germany.org -> FUTURE-INC-GERM).
Solution
When the installer finishes the base installation in the GTK dialogue and you receive the domain setup part in the browser view (where the hostname, domain, etc. is configured), simply switch to a shell by pressing CTRL-ALT-F2.
In this shell you can force the name of the NETBIOS value within the installation envrionment with the help of chroot and the ucr force-scope:
chroot /target /bin/bash
ucr set --force windows/domain="NEW-NETBIOS"
Switch back with CTRL-ALT-F5 and continue.
I you need more information regarding this issue you can also consider:
If you already installed UCS and need to change the NetBIOS name afterwards, have a look at: