nginx: [emerg] unknown "name" variable, nginx: [emerg] unknown "ssl_preread_server_name" variable

i'm trying to set up my own Stealth VPN server using NGINX 1.18 in Debian 11. I follow this guide but many of the directives are not working. The problem is when i issue nginx -t test command the output is:

 - nginx: [emerg] unknown "ssl_preread_server_name" variable

I changed this varaible from $ssl_preread_server_name to $server_name if the problem is only with this particular variable and to see if there are any other erros, the test has passed but found another variable error, this one:

 - nginx: [emerg] unknown "name" variable`

Which is in my last server block of code in nginx.conf file os i don't expect it to find any more errors. I checked the original datase of Nginx variables and the variable $name and $ssl_preread_server_name are official and exist. The guide i follow said they should be allocated like this and there are not any other guides on the internet so i'm kinda stuck.

So far i have just problem with those two variables. The are located in map block and last server block. Thank you very much for your help

This is my whole code:

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections 768;
    # multi_accept on;
}

http {

    ##
    # Basic Settings
    ##

    sendfile on;
    tcp_nopush on;
    types_hash_max_size 2048;
    # server_tokens off;

    # server_names_hash_bucket_size 64;
    # server_name_in_redirect off;

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

    ##
    # SSL Settings
    ##

    ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3; # Dropping SSLv3, ref: POODLE
    ssl_prefer_server_ciphers on;

        ssl_certificate /etc/ssl/certs/nginx-selfsigned.crt;
        ssl_certificate_key /etc/ssl/private/nginx-selfsigned.key;

        ##
        # Servers
        ##
        
        server {
            # server_name 206.189.21.228;
              listen 127.0.0.1:8000;
        }

        ##
        # map
        ##

        map $ssl_preread_server_name $name {
            default https;
            206.189.21.228 vpn;
        }

    ##
    # Logging Settings
    ##

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    ##
    # Gzip Settings
    ##

    gzip on;

    ##
    # Virtual Host Configs
    ##

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}

stream { 
     ssl_certificate /etc/ssl/certs/nginx-selfsigned.crt;
     ssl_certificate_key /etc/ssl/private/nginx-selfsigned.key;
    
     upstream https {
         server unix:/etc/nginx/nginx_writing;
         }
    
     upstream vpn {
         server unix:/etc/openvpn/openvpn_writing;
     }
    
     server {
         listen unix:/etc/nginx/nginx_writing ssl;
         # openvpn doesn't support unix-sockets
         proxy_pass 127.0.0.1:1194;
     }
    
     server {
         listen unix:/etc/nginx/nginx_writing2 ssl;
         # could also use a unix-socket here
         proxy_pass 127.0.0.1:8000;
     }
    
    server { 
        listen [::]:443 ipv6only=off;
        proxy_protocol on;
        proxy_pass $name;
    }

}

The issue is that your nginx does not have the required ngx_stream_ssl_preread module. You need to find an nginx build that has this module included.