Got it!
My theory that rest980 was occupying the MQTT connection was correct. Once I shut down the rest980 instance, I was able to connect using this Python script:
https://github.com/koalazak/dorita980/issues/10#issuecomment-296666429
When reviewing that code, I noticed that the client ID was set to the blid, which matched what I saw in the dorita980 code. That appears to have been a crucial piece. Once I made that change, I was able to connect with MQTT Explorer.
Next step is to work on the driver in Hubitat!
