Custom ptvo device with UART spams MQTT with retained Home Assistant trigger config messages

[ondras12345]

Hi,
I have a custom CC2530-based device that receives UART messages (every 30 seconds) and forwards them via zigbee. Whenever a UART message is received, zigbee2mqtt sends (among others) a MQTT message like this:

homeassistant/device_automation/0x00124b000cbe08e1/action_50,48,50,52,48,55,50,55,84,49,55,52,57,50,49,90,9,32,32,32,32,32,50,55,49,52,56,9,32,51,52,46,32,54/config {"automation_type":"trigger","device":{"configuration_url":"http://zigbee2mqtt.rpi.lab.lan//#/device/0x00124b000cbe08e1/info","identifiers":["zigbee2mqtt_0x00124b000cbe08e1"],"manufacturer":"Custom devices (DiY)","model":"Multi-functional device (ptvo.switch)","name":"elektromer","sw_version":"2024-05-23","via_device":"zigbee2mqtt_bridge_0x00124b0024c750a9"},"origin":{"name":"Zigbee2MQTT","sw":"1.39.0","url":"https://www.zigbee2mqtt.io"},"payload":"50,48,50,52,48,55,50,55,84,49,55,52,57,50,49,90,9,32,32,32,32,32,50,55,49,52,56,9,32,51,52,46,32,54","subtype":"50,48,50,52,48,55,50,55,84,49,55,52,57,50,49,90,9,32,32,32,32,32,50,55,49,52,56,9,32,51,52,46,32,54","topic":"zigbee2mqtt/elektromer/action","type":"action"}

(50,48,50,52,48,55,50,55,84,49,55,52,57,50,49,90,9,32,32,32,32,32,50,55,49,52,56,9,32,51,52,46,32,54 is the content of the UART message represented as a series of ASCII values.)
Presumably, this is is configuration for an MQTT device trigger in Home Assistant. However, Home Assistant does not seem to offer me such a device trigger -- and even if it did, I don't need that. Each UART message will be different (it contains a timestamp), so this just spams my MQTT broker with useless messages with retain flag set.

How can I prevent this?
For now, I have created a Home Assistant automation that subscribes to homeassistant/device_automation/0x00124b000cbe08e1/# and erases the messages by sending an empty retained message to the same topic. However, this is just a temporary solution.

Edit - related message from Home Assistant log:

2024-07-27 20:17:14.262 WARNING (MainThread) [homeassistant.components.mqtt.discovery] Received message on illegal discovery topic 'homeassistant/device_automation/0x00124b000cbe08e1/action_50,48,50,52,48,55,50,55,84,49,56,49,54,53,49,90,9,32,32,32,32,32,50,57,53,57,52,9,32,51,53,46,32,57/config'. The topic contains not allowed characters. For more information see https://www.home-assistant.io/integrations/mqtt/#discovery-topic

[ondras12345]

I have generated a new firmware using ptvo-2024-10-01, set a custom model and generated a .js file, which I then added in zigbee2mqtt as an external converter. I force deleted the old device, restarted zigbee2mqtt and re-paired.
However, this did not help. Zigbee2mqtt still publishes thoese action MQTT messages that Home Assistant complains about.