Just upgraded HA to 2025.3.2 and the temperature readings are back 
.
The warning logged in HA log file is now:
(<class āhomeassistant.components.mqtt.sensor.MqttSensorā>) is using native unit of measurement āCā which is not a valid unit for the device class (ātemperatureā) it is using; expected one of [āĀ°Cā, āKā, āĀ°Fā]
Might be related to this PR (Update temperature units to Ā°C by stas-demydiuk Ā· Pull Request #11 Ā· igor-podpalchenko/ha-devi-mqtt Ā· GitHub) which has not yet been merged in the addon (GitHub - bob-tm/ha-devireg-mqtt-addon).
Edit: Ok I read the whole topic and just now understand that @Qa23 is the author of the addon :D, so probably aware of this PR.