You can follow this article pretty much all the way.
https://techjogging.com/redirect-www-to-https-in-synology-nas-nginx.html
However, it will fail if you use Letsencrypt to generate an SSL Certificate. So you simply need to add the following above the redirect line. Here’s how it should look.
server {
listen 80 default_server{{#reuseport}} reuseport{{/reuseport}};
listen [::]:80 default_server{{#reuseport}} reuseport{{/reuseport}};
gzip on;
location /.well-known/acme-challenge/ {
# put your configuration here, if needed
}
server_name _;
return 301 https://$host$request_uri;
}
Of course after you make this change you will need to restart Nginx
synoservicecfg --restart nginx
You can add as many locations as you like; once they’re matched, the request will not continue to the redirect at the end of the server {} container.
This was highlighted in the following Stack Overflow post.
https://serverfault.com/questions/874090/nginx-redirect-everything-except-letsencrypt-to-https