Auto-update obviously.

Which introduces new security risks, but more importantly, the consumer has to configure the device to use open source firmware, and set up auto updates, unless the device is being auto updated by the device manufacturer and forces all of their customers to switch to the new firmware, which seems very unlikely.

How? The device phones home to the manufacturer's servers to get new updates. Manufacturer goes out of business, servers get shut down. How does it know where to get updates now?