What did you try and what was the error?

How are u running it? Bare metal? Docker?

So nginx, traffic, and cloudflare are both reverse proxies that can do SSL termination. Now cloudflare hijacks all SSL connection it proxies (essentially a mitm) and has configuration for if u would like SSL connection from cloudflare to ur own server.

All reverse proxies pass along headers to backend services indicating all sorts of things most importantly the remote client IP, and info about if the service is behind an ssl proxy.

I use client -> cloudflare -> nginx -> my services. The client makes an encrypted pipe between itself and cloudflare, cloudflare then terminates SSL does some scanning on the raw unencrypted packet makes an encrypted connection to nginx and attaches headers about the client. I have a SSL cert on my server where nginx does SSL termination of the cloudflare connection. Nginx then attaches more headers and does routing to passes it back to a backend service ie searxng (the service itself) the docker compose for searxng comes with a packaged traffic reverse proxie its not necessary here and will in fact cause all sorts of problems.

Here is the service in my docker compose for searxng:

searxng:
    container_name: searxng
    image: docker.io/searxng/searxng:latest
    restart: unless-stopped
    networks:
      - local_bridge
      - proxy
    volumes:
      - ./data/searxng:/etc/searxng
    environment:
      - SEARXNG_BASE_URL=https://${SEARXNG_HOSTNAME:-localhost}/
      - SEARXNG_SECRET=${SEARXNG_SECRET}
    cap_drop:
      - ALL
    cap_add:
      - CHOWN
      - SETGID
      - SETUID

Here is the docker compose for my nginx config

  certbot:
    image: certbot/dns-cloudflare
    # Command to obtain certificates (run once manually or integrate with a web server's startup)
    # Replace 'yourdomain.com' and '*.yourdomain.com' with your actual domain(s)
    volumes:
      - ./data/certbot/conf:/etc/letsencrypt
      - ./data/certbot/www:/var/www/certbot # A dummy webroot, not strictly necessary for DNS challenge but good practice
      - ./data/certbot/secrets:/etc/letsencrypt/secrets:ro # Mount secrets read-only
    command: certonly