Where is the old UI?

[hmerk (Hans-Jörg Merk)]

@rlkoshak answered the question here

Integration OH3 and HomeAssistant via MQTT binding

Is the online/offline message retained? Those MQTT Explorer screen shots seems to indicate that it is not. Unless OH happened to be connected to the LWT topic at the time that the online message was sent from HA, OH doesn’t know whether the end device is online or not so it defaults to offline. LWT messages like this should always be retained.