Add user, who start with number, failed

[Bob]

commandline works:
sudo useradd -d /home/4Syno -m 4Syno
sudo passwd 4Syno

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-control-center 1:3.36.4-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
CurrentDesktop: ubuntu:GNOME
Date: Mon Oct 5 17:35:52 2020
ExecutablePath: /usr/bin/gnome-control-center
LiveMediaBuild: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: gnome-control-center
UpgradeStatus: No upgrade log present (probably fresh install)

[Bob (4syno)]

syslog:

Add users who start with a number failed:
Oct 5 17:05:10 ubuntu accounts-daemon[8794]: adduser: Please enter a username m
atching the regular expression configured
Oct 5 17:05:10 ubuntu accounts-daemon[8794]: via the NAME_REGEX[_SYSTEM] config
uration variable. Use the `--force-badname'
Oct 5 17:05:10 ubuntu accounts-daemon[8794]: option to relax this check or reco
nfigure NAME_REGEX.

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1630417, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.