KevinTheJedi Thanks for the reply; as far as I can tell both the broken and working language packs all have the same owner and permissions:
###@### i18n % ls -l
total 3264
-rwxrwxr-x@ 1 _www _www 1097 8 Mar 19:56 README.md
-rw-r--r--@ 1 _www _www 408322 19 Maj 22:25 da.phar
-rw-r--r--@ 1 _www _www 402436 19 Maj 22:25 en_GB.phar
drwxrwxr-x@ 25 _www _www 800 15 Maj 11:56 en_US
-rwxrwxr-x@ 1 _www _www 20586 8 Mar 19:56 langs.php
-rw-r--r--@ 1 _www _www 402649 19 Maj 22:25 no.phar
-rw-r--r--@ 1 _www _www 420802 19 Maj 22:25 sv_SE.phar
drwxrwxr-x@ 3 _www _www 96 15 Maj 11:56 vendor
Same goes for extended attributes:
###@### i18n % xattr *.phar
da.phar: com.apple.quarantine
en_GB.phar: com.apple.quarantine
no.phar: com.apple.quarantine
sv_SE.phar: com.apple.quarantine
Both httpd and php are running as _www:
###@### i18n % ps aux | egrep 'httpd|php'
_www 41579 0,0 0,0 34655212 1276 ?? S 12:47am 0:00.00 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 41293 0,0 0,1 34928376 23748 ?? S 11:08pm 0:00.17 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 41292 0,0 0,1 34823864 22296 ?? S 11:07pm 0:00.09 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 41291 0,0 0,1 34804472 23696 ?? S 11:07pm 0:00.18 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 41290 0,0 0,1 34945720 25060 ?? S 11:07pm 0:00.15 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 41289 0,0 0,1 34928312 23280 ?? S 11:07pm 0:00.17 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 41288 0,0 0,1 34804472 30664 ?? S 11:07pm 0:00.40 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
root 41287 0,0 0,1 34645020 18140 ?? Ss 11:07pm 0:00.36 /usr/local/opt/httpd/bin/httpd -D FOREGROUND
_www 39479 0,0 0,0 34661020 1092 ?? S 10:49pm 0:00.00 php-fpm: pool www
_www 39478 0,0 0,0 34643612 1152 ?? S 10:49pm 0:00.00 php-fpm: pool www
root 39477 0,0 0,0 34642636 14980 ?? Ss 10:49pm 0:00.38 php-fpm: master process (/usr/local/etc/php/8.1/php-fpm.conf)
Also, forgot to mention in the OP that the server is an Intel-based Mac Pro running macOS 12.6.6, with the Homebrew builds of httpd, PHP and MariaDB.