"Support for open firmware is, arguably, a niche consideration at the moment"
It is at the moment, that's true. However, I am only buying "smart" stuff if and when I know beforehand that I can install some sort of supported open OS/firmware on it. I am also preaching this to everyone I know who is not out of earshot within three seconds. And indeed, there is (growing) interest for this idea even in circles that I can only describe as technically challenged. What's needed beyond that interest is a way to install/update these things in a manner that is so easy that those people are willing to do it.