OK, I've figured out the mystery at home - after everything I could find, and turned it off, finally thought to unplug it. That worked. Letting it sleep, with the window down, it was finally silent. Also confirmed that whirring returns the instant I turn on outlets. But two things: 1 - that...
I literally did the exact same thing this morning haha. It did not help in my case. I'm not trying to keep any accessory on whatsoever: these are all the things I've turned off yet it whirs away - Sentry, AC Outlets, DC accessory outlets, Power Share, Auto Dashcam, and Cabin Overheat