AceFour

So not sure what you are using for proxy. I am using Caddy which will make a certificate for you.

I have Cloudflare for DNS and point it to my in-home router and is set to Proxy status to DNS only. The in-home router points to my box for 443.

Spin up and go to privatebin.mydomain.tld

./data/caddy/Caddyfile

{
	email myemail@gmail.com
}
privatebin.mydomain.tld{
	reverse_proxy privatebin:8080
}

docker_compose.yml

version: "3.9"

networks:
  web:
    external: true
  caddy_internal:
    external: false
    driver: bridge

services:
  caddy:
    image: caddy:latest
    restart: unless-stopped
    container_name: caddy
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./data/caddy/Caddyfile:/etc/caddy/Caddyfile
      - ./data/caddy/data:/data # Optional
      - ./data/caddy/config:/config # Optional
    networks:
      - web
      - caddy_internal
  privatebin:
    image: privatebin/nginx-fpm-alpine:latest
    restart: unless-stopped
    container_name: privatebin
    volumes:
      - ./data/privatebin:/srv/data
    networks:
      - caddy_internal