> Home Assistant used to have plugins for zwave and zigbee but they are now replaced by an MQTT broker that sits between Home Assistant and the program driving the wireless dongle

And now, they've moved on from that to having straight websocket communication between those two programs, eliminating MQTT altogether.

I use MQTT for a lot of stuff but it adds a layer of delay between devices that is particularly noticeable with flipping a light switch in the Home Assistant web ui.