"sort" does not perform correctly when locale is en_GB or en_US

[Howard Houzuo Guo]

Create a plain text file with two lines:

a1 12
a 12

Sort it using locale "C", observe the correct result:

env LC_ALL=C sort test.txt
a 12
a1 12

Sort it using other English locales and observe the incorrect result:

env LC_ALL=en_US sort test.txt
a1 12
a 12
env LC_ALL=en_GB sort test.txt
a1 12
a 12

The system has the following locales packages installed:

ii locales 2.31-0ubuntu9 all GNU C Library: National Language (locale) data [support]
ii locales-all 2.31-0ubuntu9 amd64 GNU C Library: Precompiled locale data

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: coreutils 8.30-3ubuntu2
ProcVersionSignature: Microsoft 4.4.0-18362.836-Microsoft 4.4.35
Uname: Linux 4.4.0-18362-Microsoft x86_64
ApportVersion: 2.20.11-0ubuntu27.3
Architecture: amd64
CasperMD5CheckResult: skip
Date: Tue Jul 14 12:36:53 2020
ProcEnviron:
 LANGUAGE=en_GB.UTF-8
 TERM=tmux-256color
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/usr/bin/fish
SourcePackage: coreutils
UpgradeStatus: No upgrade log present (probably fresh install)