MariaDB on host and Docker container

Hello, I have a Laravel project that connects to a MariaDB database. I don't want to use a MariaDB container. I have installed MariaDB on the host and added the following line to the /etc/mysql/mariadb.conf.d/50-server.cnf file:

bind-address = 0.0.0.0

MariaDB is running on the host:

# netstat -tulnp | grep 3306
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      3172972/mariadbd 

I edited the `.env` file as follows:

DB_CONNECTION=mysql
DB_HOST=127.0.0.1
DB_PORT=3306
DB_DATABASE=laravel_db
DB_USERNAME=root
DB_PASSWORD=123456

I also changed the `database.php` file of the Laravel project as follows:

 'mariadb' => [
            'driver' => 'mariadb',
            'url' => env('DB_URL'),
            'host' => env('DB_HOST', '127.0.0.1'),
            'port' => env('DB_PORT', '3306'),
            'database' => env('DB_DATABASE', 'laravel_db'),
            'username' => env('DB_USERNAME', 'root'),
            'password' => env('DB_PASSWORD', ''),
            'unix_socket' => env('DB_SOCKET', ''),
            'charset' => env('DB_CHARSET', 'utf8mb4'),
            'collation' => env('DB_COLLATION', 'utf8mb4_unicode_ci'),
            'prefix' => '',
            'prefix_indexes' => true,
            'strict' => true,
            'engine' => null,
            'options' => extension_loaded('pdo_mysql') ? array_filter([
                PDO::MYSQL_ATTR_SSL_CA => env('MYSQL_ATTR_SSL_CA'),
            ]) : [],
        ],

The compose file looks like this:

services:
  frontend:
    container_name: frontend
    build:
      context: /home/dev/frontend
      dockerfile: Dockerfile
    environment:
      - NODE_ENV=development
      - CHOKIDAR_USEPOLLING=true  
      - WATCHPACK_POLLING=true   
    volumes:
      - /home/dev/frontend:/app
      - /app/node_modules          
    ports:
      - "127.0.0.1:3000:3000"              
    networks:
      - app_network
    deploy:
      resources:
        limits:
          cpus: '1.0'
          memory: 512M

  # Laravel Backend
  backend:
    build:
      context: /home/dev/portal
      dockerfile: Dockerfile
    container_name: backend
    entrypoint: ["/usr/local/bin/entrypoint.sh"]
    command: ["php-fpm"]
    environment:
      APP_ENV: local
      APP_DEBUG: "true"
      DB_HOST: host.docker.internal
      DB_PORT: 3306
      DB_DATABASE: laravel_db
      DB_USERNAME: root
      DB_PASSWORD: 123456
      XDEBUG_CONFIG: "client_host=host.docker.internal client_port=9003"
    volumes:
      - /home/dev/portal:/var/www
    networks:
      - app_network
    ports:
      - "9000:9000"
    extra_hosts:
      - "host.docker.internal:host-gateway"

networks:
  app_network:
    driver: bridge

After these settings, I ran the containers and connected to the backend container:

# docker exec -u root -it backend bash
#
# nc HOST_IP -v 80
Ncat: Version 7.93 ( https://nmap.org/ncat )
Ncat: Connected to 172.20.2.58:80.
#
# nc HOST_IP -v 3306
Ncat: Version 7.93 ( https://nmap.org/ncat )
Ncat: No route to host.

As you can see, from inside the container I can connect to port 80 which is for Nginx, but I can't connect to MariaDB.

Which part of the settings is wrong?

Thank you.