location = /downloads/ {
        root /srv;
        autoindex on;
    }

    location ~ ^/downloads/.*/$ {
        root /srv;
        autoindex on;
    }

    location ~ ^/downloads/(.*)$ {
        root /srv/downloads;
        try_files /astra/$1
                  /genio/$1
                  /mediatek/$1
                  /synaptic/$1
                  =404;
        autoindex on;
    }