Strange behavior for mqtt discovery/configuration.yaml

Hello all !
I’m trying to setup a docker version for HASS and so far I’ve been able to install and configure HASS itself and the MQTT broker ( also in separate docker ) and is somehow working. ( I’m on RPi 4 but is working with quite a bunch of other dockers, and for now I would not like to get a single RPi just for HASS )
The only thing, at the moment, I’m fighting with is that I can’t get a stable configuration for the MQTT.
The only sensor I have for now is a simple ESP32 board reading power and sending out the reading via MQTT protocol.
My configuration.yaml looks like this:

# Configure a default setup of Home Assistant (frontend, api, etc)

# Text to speech
  - platform: google_translate

group: !include groups.yaml
automation: !include automations.yaml
script: !include scripts.yaml
scene: !include scenes.yaml

  port: 1883
  client_id: home-assistant
  username: mqtt_user
  password: mqtt_password
  discovery: false

  - platform: mqtt
    name: IoT-En-Mon
    state_topic: "homeassistant/sensor/IoTEnMon/state"
    unit_of_measurement: "W"
    unique_id: mqtt_iotenmon
    device_class: power
    value_template: "{{ states('sensor.pv_power') | float }}"

thus, trying to not make mqtt discover and work with my indications.
What happens is that HASS does not collect values from this one, and after a while it create a new device “IoTEnMon” ( with no unique_id ) and collect values only from this one.
Not a big problem as I can use this one for my dasboard and statistics but… if I restart the home-assistant itself, then for quite a while the (discovered) sensor is missing:

Here an image from entities after a restart:

And this is the image after few minutes with the new dicovered sensor:

It’s clearly my bad in configuration, but can you help in finding what I’m doing wrong here ?
I only would like to get info from the one I’ve configured by hand :slight_smile:, and being that sometimes my RPi reboot, I would like to get values back as soon as possible :slight_smile: