sftpgo-docker-compose.yaml

version: "3"
services:
  sftpgo:
    image: "drakkan/sftpgo:v2-alpine"
    # default user id
    user: 1026
    restart: always
    expose:
      # HTTP
      - "8080"
      # HTTPS
      - "443"
      # WebDav
      - "5007"
    environment:
      # These are the settings to access your db
      SFTPGO_WEBDAVD__BINDINGS__0__PORT: 5007
      SFTPGO_DATA_PROVIDER__DRIVER: "mysql"
      SFTPGO_DATA_PROVIDER__NAME: "sftpgo"
      SFTPGO_DATA_PROVIDER__HOST: "mysql"
      SFTPGO_DATA_PROVIDER__PORT: 3306
      SFTPGO_DATA_PROVIDER__USERNAME: "<SQL_USER>"
      SFTPGO_DATA_PROVIDER__PASSWORD: "<SQL_PASS>"
      SFTPGO_COMMON_DEFENDER__ENABLED: "true"
      SFTPGO_COMMON_DEFENDER__BAN_TIME: 15
      SFTPGO_COMMON_DEFENDER__BAN_TIME_INCREMENT: 100
      SFTPGO_COMMON_DEFENDER__THRESHOLD: 5
      SFTPGO_COMMON_DEFENDER__OBSERVATION_TIME: 15
    volumes:
      - ./:/srv/sftpgo
  mysql:
    image: mysql:latest
    restart: always
    environment:
      MYSQL_DATABASE: "sftpgo"
      MYSQL_USER: "<SQL_USER>"
      MYSQL_PASSWORD: "<SQL_PASS>"
      MYSQL_ROOT_PASSWORD: "<SQL_ROOT_PASS>"
    volumes:
      - ./database:/var/lib/mysql
networks:
  default:
    external:
      name: nginx-proxy-manager_default

ERROR: The Compose file './docker-compose.yml' is invalid because: services.sftpgo.user contains an invalid type, it should be a string

I guess the user should be:
user: "1026"

SFTPGO_COMMON_DEFENDER__ENABLED is missing an additional _ between COMMON and DEFENDER. The correct labale are as follows:

SFTPGO_COMMON__DEFENDER__ENABLED: "true"
SFTPGO_COMMON__DEFENDER__BAN_TIME: 15
SFTPGO_COMMON__DEFENDER__BAN_TIME_INCREMENT: 100
SFTPGO_COMMON__DEFENDER__THRESHOLD: 5
SFTPGO_COMMON__DEFENDER__OBSERVATION_TIME: 15

Thanks Brian.