https://dev.to/stjohnjohnson/internal-domains-with-dnsmasq-and-pi-hole-4cof

docker-compose.yml

version: '3'

services:
  pihole:
    image: pihole/pihole
    hostname: pihole
    restart: unless-stopped
    ports:
      - 53:53/tcp
      - 53:53/udp
      - 80:80/tcp
    dns:
      - 127.0.0.1
      - 1.1.1.1
    volumes:
      - ./internal.conf:/etc/dnsmasq.d/02-internal.conf
      - ./internal.list:/etc/pihole/internal.list
    environment:
      ServerIP: "10.0.0.205"

internal.conf

addn-hosts=/etc/pihole/internal.list

internal.list

# This is a single domain to a server
10.0.0.210      plex.example.com

# Multiple domains can point to the same server
# (routed via different ports or a proxy like nginx)
10.0.0.205      haas.example.com
10.0.0.205      pihole.example.com

# Here is an example of short name
# (useful for things like short-url services)
10.0.0.215      go

# IPs do not need to be in your network
192.168.100.1   modem

Makefile

all: build test clean

test:
	@echo "========== Internal Domains =========="
	dig @127.0.0.1 haas.example.com +short
	dig @127.0.0.1 pihole.example.com +short
	dig @127.0.0.1 plex.example.com +short
	dig @127.0.0.1 go +short
	dig @127.0.0.1 modem +short

	@echo "========== External Domains =========="
	dig @127.0.0.1 google.com +short
	dig @127.0.0.1 github.com +short

build:
	docker-compose up -d
	until curl -f -I http://127.0.0.1; do sleep 1; done

clean:
	docker-compose down -v