While I’m not in love with proprietary software nor APIs from the start, I would accept some policy/regulation that would require smart device manufacturers to open-source the drivers after some given time.

Too many devices become obsolete software-wise then become e-waste not too long after. At least by open-sourcing you allow others to at least use the hardware, and the manufacturer benefits by saying “we didn’t just brick everything” while people who actually care to support it can do so.