Sounds like you might have tried this already, but GNOME has had a history of working on accessibility, and I think they're quite open to bugs in case something is broken. How well it works in practice, I don't know, though:
Thanks, I tried persevering with gnome for quite a while because I wanted to use Linux day-to-day. But all of the accessibility stuff at the time was a subset of all of the things that ordinary user could do, that just wasn't enough when I started working and I needed something as full featured as Apple's offering.
I mean I'm obviously going to try and change the state of accessibility and Linux by submitting bug reports and getting involved, but it's a long slow process and in the meantime I need a computer that works.
https://wiki.gnome.org/Accessibility
Fedora or Debian is probably the easiest way to get a GNOME desktop these days.