It’s perfectly possible to provide all the weather information to Home Assistant via MQTT, and I do that without a problem, but it’s all under the sensor domain, and not the weather domain. Every other common integration (switch, sensor, climate, light, cover etc) has an equivalent available via MQTT. I can’t have a pretty lovelace weather card, because the built in one, and the 3rd party ones - expect entities to be under the weather domain.