just tested in my fully -Suy'd i686 librechroot
worked fine
so I guess the question becomes what is the difference between the two

i can confirm that inside the chroot, the packages are not available (same result with `librechroot -n i686 install-name git`) - however, on an installed i686 system it succeeds, but gives a different error:

# pacman -S git
resolving dependencies...
looking for conflicting packages...

Packages (5) pcre2-10.32-1.0  perl-error-0.17027-1.0  perl-mailtools-2.20-2.1  perl-timedate-2.30-5.1  git-2.19.2-1.0

Total Download Size:    5.16 MiB
Total Installed Size:  43.62 MiB
....
:: Running post-transaction hooks...
(1/2) Warn about old perl modules
WARNING: '/usr/lib/perl5/5.28' contains data from at least 3 packages which will NOT be used by the installed perl interpreter.
 -> Run the following command to get a list of affected packages: pacman -Qqo '/usr/lib/perl5/5.28'
(2/2) Creating system user accounts...
call to execv failed (No such file or directory)
error: command failed to execute correctly
$ pacman -Ss '^git$'
extra/git 2.19.2-1 [installed]
    the fast distributed version control system

Git continues to be available and installable in my i686 chroot?

[root@freemor /]# pacman -S git
resolving dependencies...
looking for conflicting packages...

Packages (4) perl-error-0.17027-1.0  perl-mailtools-2.20-2.1  perl-timedate-2.30-5.1  git-2.19.2-1.0

Total Download Size:    0.12 MiB
Total Installed Size:  39.96 MiB

:: Proceed with installation? [Y/n] y
:: Retrieving packages...
 perl-error-0.17027-1.0-any                                                                            22.2 KiB   125K/s 00:00 [############################################################################] 100%
 perl-timedate-2.30-5.1-any                                                                            34.1 KiB  0.00B/s 00:00 [############################################################################] 100%
 perl-mailtools-2.20-2.1-any                                                                           62.5 KiB  20.4M/s 00:00 [############################################################################] 100%
(4/4) checking keys in keyring                                                                                                 [############################################################################] 100%
(4/4) checking package integrity                                                                                               [############################################################################] 100%
(4/4) loading package files                                                                                                    [############################################################################] 100%
(4/4) checking for file conflicts                                                                                              [############################################################################] 100%
(4/4) checking available disk space                                                                                            [############################################################################] 100%
:: Processing package changes...
(1/4) installing perl-error                                                                                                    [############################################################################] 100%
(2/4) installing perl-timedate                                                                                                 [############################################################################] 100%
(3/4) installing perl-mailtools                                                                                                [############################################################################] 100%
(4/4) installing git                                                                                                           [############################################################################] 100%
Optional dependencies for git
    tk: gitk and git gui
    perl-libwww: git svn
    perl-term-readkey: git svn and interactive.singlekey setting
    perl-mime-tools: git send-email
    perl-net-smtp-ssl: git send-email TLS support
    perl-authen-sasl: git send-email TLS support
    perl-mediawiki-api: git mediawiki support
    perl-datetime-format-iso8601: git mediawiki support
    perl-lwp-protocol-https: git mediawiki https support
    perl-cgi: gitweb (web interface) support
    python2: various helper scripts
    subversion: git svn
    gnome-keyring: GNOME keyring credential helper
    libsecret: libsecret credential helper [installed]
:: Running post-transaction hooks...
(1/4) Warn about old perl modules
(2/4) Reloading system manager configuration...
  Skipped: Current root is not booted.
(3/4) Creating system user accounts...
(4/4) Arming ConditionNeedsUpdate...

may be a redirector problem
the mirrir list in my i686 chrrot is different from @GNUtoo's

[root@freemor /]# cat /etc/pacman.d/mirrorlist
Server = https://repo.parabola.nu/$repo/os/$arch

i concur: the problem must be with the redirector - i just made a fresh i686 librechroot yesterday and it matches GNUtoo's

[root@bill /]# cat /etc/pacman.d/mirrorlist
Server = https://redirector.parabola.nu/$repo/os/$arch

FWIW, i think repo.parabola.nu is the appropriate "mirror", as it is the canonical replica that all other mirrors sync with - so maybe we should rename this ticket to something like: "librechroot should use the winston mirror" and move it to the libretools tracker

that o/c does not address the core issue which is: "why are some of the mirrors missing those packages for such an extended period"; which would be a different issue

i will add that, you can always specify a mirrorlist with the '-C' CLI option to `librechroot`, such as:

# librechroot -n i686 -C /path/to/custom-mirrorlist