I upgraded my sonoffs too 6.4.0. I use the german files and before 6.3.0 the LWT state was reported as ‘online’ and ‘offline’.
With the new version (to make it consistent with other languages, which always uses Online/Offline) the LWT state is reported with the first letter in upper case (Online, Offline).
With this change my lights became unavailable because I use the availability_topic, and this function only looks for online and offline in lower case letters.
So most of you guys won’t have the german version of tasmota and so you always hat Online/Offline.
How do you use the availability topic?
The workaround now for me is to comment out the availability topic (but this is a step back, and we all want to move forward with our smart homes)
After upgrade to 6.4.1, my devices constantly become unavailable in HomeAssistant. I already have “Online” and “Offline” in my configuration. It was working on 6.3.0 until I upgraded to 6.4.0 and 6.4.1