Modbus integration, write value to a hardware device on RS485 (RTU mode)

Configuration
1

I have HA 2025.12.3 on haos 16.3 on a raspberry pi 5.
I have a Waveshare USB to RTU converter.
The modbus interface is defined as:

# modbus
modbus:
  - name: modbus_hub
    type: serial
    method: rtu
    port: /dev/ttyUSB0
    baudrate: 9600
    bytesize: 8
    parity: N
    stopbits: 1
    delay: 0
    message_wait_milliseconds: 80
    timeout: 1
#

The various inputs are defined in the section “sensors:” They are provided by independant h/w devices and work okay. I can read the data and visualize it.

Also, I can write to the digital outputs defined in the section “switches:” and the attached Unipy xS51 device responds accordingly.

Now this same xS51 device has several analog outputs (16 bit registers). When I configure them using:


#
# analog outputs
#
    registers:
    # Unipi xS51 @0x05 LV1 (Analog Output 0-10V, controlled as 0-100% in UI)
      - name: LV1
        slave: 5
        address: 2
        write_type: holding
        data_type: uint16
        min_value: 0
        max_value: 100
        unit_of_measurement: "%"

the corresponding entities do not show up in the page: http://homeassistant.local:8123/config/entities

I test if the path from edit-to-page works, by renaming a resource in the section “switches:” and I see the entity change.

Now: what could be wrong with the section “registers:”?

I’d love to see your response…
Thanks in advance from Netherlands!