nginx set up for proxy_pass when ip6 and ip4 used

Is someone willing to tell me how to get this config to work?

# Define separate upstream blocks for IPv4 and IPv6 backend servers
upstream backend_ipv4_ht1 {
    server 192.168.0.1:1080;
}

upstream backend_ipv6_ht1 {
    server [2a02:8070:5181:25a0:da3a:ddff:fe28:17b]:1080;
}

upstream backend_ipv4_ht2 {
    server 192.168.0.1:2080;
}

upstream backend_ipv6_ht2 {
    server [2a02:8070:5181:25a0:da3a:ddff:fe28:17b]:2080;
}

# Map $remote_addr to the appropriate backend based on IP version
map $remote_addr $backend_ht1 {
    ~[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+ backend_ipv4_ht1;
    default backend_ipv6_ht1;
}

map $remote_addr $backend_ht2 {
    ~[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+ backend_ipv4_ht2;
    default backend_ipv6_ht2;
}

# HTTP and HTTPS server block for ht1.example.net
server {
    listen 443 ssl;
    listen [::]:443 ipv6only=off;

    server_name ht1.example.net;

    ssl_certificate /etc/letsencrypt/live/example.net/cert.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.net/privkey.pem;

    ssl_protocols TLSv1.3;

    location / {
        # Proxy to the appropriate backend based on the client's IP version
        proxy_pass http://$backend_ht1;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

# HTTP and HTTPS server block for ht2.example.net
server {
    listen 443 ssl;
    listen [::]:443;

    server_name ht2.example.net;

    ssl_certificate /etc/letsencrypt/live/example.net/cert.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.net/privkey.pem

    ssl_protocols TLSv1.3;

    location / {
        # Proxy to the appropriate backend based on the client's IP version
        proxy_pass http://$backend_ht2;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

I want that the reverse proxy proxies both the ipv4 and ipv6 addresses of my server… but the test:

nginx -t 

throws me the error:

nginx: [emerg] "upstream" directive is not allowed here in /etc/nginx/sites-enabled/example.conf:2
nginx: configuration file /etc/nginx/sites-enabled/example_config.conf test failed

Please help… Thank you :'|