I have been using the BlueIris NVR integration (from HACS) for quite some time, and it works great for triggering BI from HA. I've trying to do the opposite now: Fire off automations in HA whenever BI detects motion on one of my cameras.
I've never used MQTT before, so I'm learning as I go, but I think I have most of my setup configured properly. I've installed Mosquitto and the MQTT integration in HA. I've configured BI to connect to HA, and running "Test" in the "Edit MQTT Server" menu in BI shows a good connection and no errors. I've set my cameras to post an MQTT event when the alert is triggered (and I've verified that the alerts are in fact being triggered).
Nothing happens in HA, though. The "Motion" sensor for my camera in HA stays at "Clear." In fact, the history shows no change at all, ever.
I have the events in BI set up as follows: On Alert: MQTT Topic - BlueIris/&CAM/Status and Payload - { "type": "&TYPE", "trigger": "ON" } On Reset: Exactly the same, but change ON to OFF.
I've tried change the MQTT autodiscovery header in HA from "homeassistant" to "BlueIris," and it made no difference. The Mosquitto logs show a login from HA, so I feel like I'm close, but I'm not sure where else to look.
Edit: I installed MQTT explorer, and I've verified that the messages are making it to Mosquitto, and they appear to be correctly formatted.
UPDATE: I set the MQTT integration to listen to the MQTT messages coming from BI, and sure enough, they were coming through just fine. For some reason, the BI integration just wasn't seeing them. Digging through the system logs, I saw some errors "creating a binary sensor" coming from the BI integration. The only thing I can think is that because I didn't have MQTT set up when I first installed the BI integration, something went wrong with the config (although I had already rebooted the system several times). I re-downloaded the BI integration and re-installed it, and now everything works perfectly.
The strange part is that the BlueIris integration already has "Motion" devices for each of my cameras. The documentation made it sound like I just needed to start feeding HA with MQTT messages that these devices were expecting.
I may do like you suggested and just manually set up binary MQTT sensors. It would look a lot cleaner to tie it into the existing integration, but I'm not sure if it's worth the extra troubleshooting.