They're happy in their walled garden, until they don't and discover there is a wall they now can't overcome and learn whose hardware it really is

I do think it is in everyone's interest to be able to run software of your choosing on hardware you bought to own. The manufacturer needn't make it easy (my microwave sure didn't expect to install extra software packages; I don't expect them to open up an interface for this) but they also don't need to actively block the device owner from doing it