Although the hardware, the precursor, is more akin to a PDA than a smartphone it very well allows for mods targeting e.g. impaired vision, as the featured prototype of a braille keyboard shows.
I'm sure you've used software with open APIs with terrible accessibility too, the point is that with enough interest, open APIs make it easier to make alternate frontends. And open source implies an open API with the additional advantage of making it easier to modify the frontend.
In principle this is true, but my experience for accessiblity is: Apple first (they are amazing), Windows second (although many use 3rd party apps like JAWS), then Linux a distant third.
"What’s the Value of Hackable Hardware, Anyway?" https://www.bunniestudios.com/blog/?p=6031
Although the hardware, the precursor, is more akin to a PDA than a smartphone it very well allows for mods targeting e.g. impaired vision, as the featured prototype of a braille keyboard shows.