OMV default configuration is consuming all /**/*.php
requests. We've to exclude /pihole
php requests to forward them to pihole.
location ~ ^(?!\/pihole\/).*\.php$ {
try_files $uri =404;
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_pass unix:/run/php/php7.3-fpm-openmediavault-webgui.sock;
fastcgi_index index.php;