Apache 2.4 unixgroup authentication not working

Require unix-group is not working for me when configuring the VirtualHost for my Apache server. Whenever I log in using pwauth, the server still authenticates users who are not members of the group that I specify. The attempted changes to /etc/apache2/sites-enabled/000-default.conf can be shown below:

<VirtualHost *:80>
    ServerAdmin ratman@localhost
    DocumentRoot /var/www/aperture-apache-server

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
    
    AddExternalAuth pwauth /usr/sbin/pwauth
    SetExternalAuthMethod pwauth pipe
    
    <Directory /var/www/aperture-apache-server/employees>
            Options Indexes FollowSymLinks MultiViews
            IndexIgnore ..
            IndexOptions FancyIndexing
            DirectoryIndex index.html /employees/_h5ai/public/index.php
            
            AuthType Basic
            AuthName "Login"
            AuthBasicProvider external
            AuthExternal pwauth
            
            Require valid-user
            Require unix-group aperturestaff
    </Directory>
</VirtualHost>

So, I decided to switch away from mod_authnz_unix_group to a more primitive method: the unixgroup binary that you can install alongside pwauth. I ran chmod u+s pwauth on it and moved it to /usr/sbin/. My resultant configuration changes to /etc/apache2/sites-enabled/000-default.conf are shown below:

<VirtualHost *:80>
    ServerAdmin ratman@localhost
    DocumentRoot /var/www/aperture-apache-server

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
    
    AddExternalAuth pwauth /usr/sbin/pwauth
    SetExternalAuthMethod pwauth pipe
    AddExternalGroup unixgroup /usr/sbin/unixgroup
    SetExternalGroupMethod unixgroup environment
    
    <Directory /var/www/aperture-apache-server/employees>
            Options Indexes FollowSymLinks MultiViews
            IndexIgnore ..
            IndexOptions FancyIndexing
            DirectoryIndex index.html /employees/_h5ai/public/index.php
            
            AuthType Basic
            AuthName "Login"
            AuthBasicProvider external
            AuthExternal pwauth
            GroupExternal unixgroup
            
            Require valid-user
            Require group aperturestaff
    </Directory>
</VirtualHost>

But then, Apache fails to start, saying:

Aug 22 17:43:39 aperture-mainframe systemd[1]: Failed to start The Apache HTTP Server. Subject: A start job for unit apache2.service has failed Defined-By: systemd Support: http://www.ubuntu.com/support A start job for unit apache2.service has finished with a failure. The job identifier is 2860 and the job result is failed.

Please help me configure group-based authentication on my Apache server (no, I do not want to use a .htpasswd file for protecting this directory, I want it done via VirtualHost)! I am using Ubuntu 22.04 LTS.