https://wiki.debian.org/accessibility https://www.debian.org/devel/debian-accessibility/software
ORCA is probably the strongest FOSS competitor of JAWS:
https://wiki.debian.org/Orca https://help.gnome.org/users/orca/stable/
I don't know whether Debian would be the best choice for OP or not. In my experience, I wouldn't install any new OS for someone unless you are willing and available to help the person until they get the hang of it.
My parents have been using Linux (formerly Debian and now Mint) for over a decade after they got fed up with Windows. I still have to help them from time to time, but I think that would also be the case with Windows, except I would be trying to remove malware instead of showing them how to burn a DVD or what have you.