So I’m definitely not using the Distributed Gateway settings in Govee. However, I did connect Google Home to Govee so I’d be able to control my smart plugs (this was before I had HA)! So maybe that’s it? Google Home → Settings → Services → Works with Google → Added Govee.
I followed this guide exactly to get Mosquitto up and running: https://github.com/home-assistant/addons/blob/8ccd6c40beb7d32a7e6ecf5472abc6bbd965ed26/mosquitto/DOCS.md
. Of note, I did to the step that said "Create a new user for MQTT via your Home Assistant’s frontend Settings → People → Users " —> but I don’t necessarily remember putting those creds anywhere in any configuration 
As for anonymous login, based on this topic, I’m fairly certain I don’t have anonymous logins turned on.