Creating devices in Home Assistant

Hi guys,
first post so apologies if I missed any etiquette.
I got OMG installed on a WEMOS ESP32 board and integrated it in HA ( esp32dev-ble, v0.9.9).
I also have a LYWSD03MMC flashed with the custom firmware (pvvx flavour), HW B1.7, SW 3.5.
All settings are default (except for the name: “ATC_CF0001”), i.e. Advertising type is set to “Custom”.

MQTT Explorer connected to the mosquitto on HA show the following for the ID/MAC:
{
“id”: “A4:C1:38:CF:01:56”,
“mac_type”: 0,
“name”: “ATC_CF0001”,
“rssi”: -70,
“servicedata”: “5601cf38c1a44008bd13470c64cc0f”
}

If I understand BLE gateway | OpenMQTTGateway v0.9.9 correctly, the sensor values should show up in MQTT as well (lux in the example), but that isn’t the case.

SYS:Autodiscovery is on in HA.
Any ideas what to try next?

GitHub - atc1441/ATC_MiThermometer: Custom firmware for the Xiaomi Thermometer LYWSD03MMC and Telink Flasher via USB to Serial converter also says it works OOTB regarding autodiscovery, but I only have the OMG itself, not the sensor.
I assume that relies on the OMG “converting” the advertised values so should work then.