It’s possible to customize the vhosts php-fpm, see also GitHub - NethServer/ns8-webserver: A webserver (nginx based) with php-fpm stack
In this example the first vhost using php8.3 with user 9001 of the webserver1 app instance is customized. Please adapt php version, user id and instance to match your case.
Run nano in the webserver1 app environment to create/edit the file php8.3-fpm-custom.d/dyn-9001.custom
runagent -m webserver1 nano php8.3-fpm-custom.d/dyn-9001.custom
Add following content to set your wanted size:
php_admin_value[upload_max_filesize]=3000M
php_admin_value[post_max_size]=3000M
EDIT:
Restart php-fpm 8.3 to apply the new config:
systemctl --user restart phpfpm@8.3