Periodically, I scan the 'net looking for acceptable speech-to-text options for Linux and never really find anything that works all that well - for me. You may find something else, but to me all the options were either a bit obscure or were more of a kludge.
Granted, it has been a couple of years since I sat down and really tried to find a solution.
On the other hand, I can easily do speech-to-text on any of my Android devices. As much as I love Linux, it's not always the best solution. So, there's something to think about.
But, let's be optimistic... Things may have changed in the past couple of years since I last devoted a day to testing all the solutions I could find. If not, you may wish to look in the direction of Android - tablets, tablets with keyboards, and presumably Chrome (the OS) (eg Chromebooks) are perhaps better solutions for someone who is disabled.