You could try my nginx configuration file
Config model1:

# if you need to change from http to https
server {                                                                                                                                
    if ($host = yourhost.net) {                                                                                                   
        return 301 https://$host$request_uri;                                                                                           
    }                                                                                                                                                                                                                                             

        listen 80;                                                                                                                      
        listen [::]:80;                                                                                                                 
        server_name yourhost.net;                                                                                                 
        return 302 https://$server_name$request_uri;                                                                                                                                                                                                                           
}
# stuff here
server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;                                                                                                      
        server_name yourhost.net;                                                                                                 
        location / {
                alias /var/www/html/;
                try_files $uri $uri @fwdbackend;
        }
        location @fwdbackend {
                proxy_pass http://10.10.0.3:81;
                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;
                real_ip_header CF-Connecting-IP; # Cloudflare 
        }

Explanation:
the nginx server access file on localhost at /var/www/html/
its using alias so when http://yourhost.net/assets/x.js will looking into /var/www/html/assets/x.js
and when there’s no file match with the user request it’ll pass to @fwdbackend (which pass the user request to 10.10.0.3:81 [nodejs server])

Config model2"

server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;                                                                                                      
        server_name yourhost.net;                                                                                                 
        location /assets {
                alias /var/www/html/assets/;
                try_files $uri $uri =404;
        }
        location / {
                proxy_pass http://10.10.0.3:81;
                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;
                real_ip_header CF-Connecting-IP; # Cloudflare 
        }

Hi, kapa.

Did you find the solution for this problem?