Activecollab 5 nginx configuration (with php-fastcgi). I'm not an expert here at all. I managed to make it all work. YMMV.

fastcgi_params

fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;
fastcgi_param  HTTPS              $https if_not_empty;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param  REDIRECT_STATUS    200;

nginx.conf

# For more information on configuration, see:
#   * Official English Documentation: http://nginx.org/en/docs/
#   * Official Russian Documentation: http://nginx.org/ru/docs/

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

events {
    worker_connections 1024;
}

http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 2048;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;

    server {
        listen       80 default_server;
        listen       [::]:80 default_server;
        server_name  _;
        root         /var/activecollab/public;
        index        index.php

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        location / {
            if (!-e $request_filename) {
                rewrite ^/assets/(.*)$ /assets/$1 last;
                rewrite ^/avatars/(.*)$ /avatars/$1 last;
                rewrite ^/wallpapers/(.*)$ /wallpapers/$1 last;
                rewrite ^/verify-existence$ /verify.php last;
                rewrite ^/proxy.php$ /proxy.php last;
                rewrite ^/api/v([0-9]*)/(.*)$ /api.php?path_info=$2&api_version=$1 last;
                rewrite ^$ /router.php last;
                rewrite ^(.*) /router.php?path_info=$1 last;
            }
        }

        location ~ \.php$ {
            include /etc/nginx/fastcgi_params;
            fastcgi_pass 127.0.0.1:9000;
            fastcgi_intercept_errors on;

            if (!-e $request_filename) {
                rewrite ^(.*) /router.php?path_info=$1 last;
            }
        }
    }
}