THIS A DRAFT I NEED TO CHECK SETTINGS
You need to have installed
- 
Nginx dietpi-software install 85
- Transmission
- Generated Certbot certificate
Create file in /etc/nginx/sites-dietpi/transmission.conf
sudo nano /etc/nginx/sites-dietpi/transmission.conf
Copy this text to transmission.conf file
location /transmission/ {
        proxy_read_timeout 300;
        proxy_pass_header  X-Transmission-Session-Id;
        proxy_set_header   X-Forwarded-Host $host;
        proxy_set_header   X-Forwarded-Server $host;
        proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
        # if you changed the port number for transmission daemon, then adjust the
        # folllowing line
        proxy_pass         http://127.0.0.1:9091/transmission/web/;
        }
        # Also Transmission specific
    location /rpc {
        proxy_pass         http://127.0.0.1:9091/transmission/rpc;
    }
Restart nginx service
sudo dietpi-services restart nginx
Go to https://YourDietpi-IP/transmission address in Web browser