The "Librem is to iPhone as Stable Diffusion is to DALL-E" analogy breaks down when you consider that Librem phone works about 10% as well as an iPhone, whereas SD works 110% as well as DALL-E.
"open source" hardware is never going to work the same way as open source software does. Hardware is fundamentally capital-intensive to produce. Software can be produced (compiled) using hardware that many people have readily available. This is a fundamental, intractable difference.
It's the difference between free knitting patterns and free cardigans.
Pixel exists (but apparently doesn't count because it's not perfect yet).
Librem exists.
PinePhone exists.
More will exist in the future.