Example with 3 Kibana instances with LB

docker-compose.yml

---
version: '3'
services:
  elasticsearch:
    container_name: es01
    image: docker.elastic.co/elasticsearch/elasticsearch:8.10.2
    environment: ['ES_JAVA_OPTS=-Xms2g -Xmx2g','bootstrap.memory_lock=true','discovery.type=single-node','xpack.security.enabled=false', 'xpack.security.enrollment.enabled=false']
    ports:
      - 9200:9200
    networks:
      - elastic
    ulimits:
      memlock:
        soft: -1
        hard: -1
      nofile:
        soft: 65536
        hard: 65536

  kib01:
    image: docker.elastic.co/kibana/kibana:8.10.2
    container_name: kib01
    environment:
      - SERVER_HOST=0.0.0.0
      - SERVER_PORT=5601
      - SERVER_NAME=kib01
      - SERVER_PUBLICBASEURL=http://localhost
      - XPACK_REPORTING_ROLES_ENABLED=false
      - XPACK_REPORTING_KIBANASERVER_HOSTNAME=localhost
      - XPACK_SECURITY_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
      - XPACK_REPORTING_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
      - XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
    ports:
      - 5601:5601
    networks:
      - elastic

  kib02:
    image: docker.elastic.co/kibana/kibana:8.10.2
    container_name: kib02
    environment:
      - SERVER_HOST=0.0.0.0
      - SERVER_PORT=5602
      - SERVER_NAME=kib02
      - SERVER_PUBLICBASEURL=http://localhost
      - XPACK_REPORTING_ROLES_ENABLED=false
      - XPACK_REPORTING_KIBANASERVER_HOSTNAME=localhost
      - XPACK_SECURITY_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
      - XPACK_REPORTING_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
      - XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
    ports:
      - 5602:5602
    networks:
      - elastic

  kib03:
    image: docker.elastic.co/kibana/kibana:8.10.2
    container_name: kib03
    environment:
      - SERVER_HOST=0.0.0.0
      - SERVER_PORT=5603
      - SERVER_NAME=kib03
      - SERVER_PUBLICBASEURL=http://localhost
      - XPACK_REPORTING_ROLES_ENABLED=false
      - XPACK_REPORTING_KIBANASERVER_HOSTNAME=localhost
      - XPACK_SECURITY_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
      - XPACK_REPORTING_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
      - XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY=super_secret_key_with_for_kibana_settings
    ports:
      - 5603:5603
    networks:
      - elastic
  nginx:
    depends_on:
      - kib01
      - kib02
      - kib03
    container_name: lb_nginx
    image: nginx
    ports:
      - "80:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
    networks:
      - elastic
networks:
  elastic:

nginx.conf

worker_processes 1;

events {
    worker_connections 1024;
}

http {
    upstream kibana {
        server kib01:5601;
        server kib02:5602;
        server kib03:5603;
    }

    server {
        listen 80;

        location / {
            proxy_pass http://kibana;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
        }
    }
}

Watching who is reporting on LB:

watch -n 0.5 "curl -s http://localhost/api/status | jq ."