There's a closed pull request on the void-packages repository

new package: espeak-ng-1.50
https://github.com/void-linux/void-packages/pull/27193

Description:
Speech Dispatcher and espeakup were also corrected to build against the new espeak-ng
  I used dummy packages to replace Espeak on installed machines. The idea was gained from polkit-elogind, however, I am open to doing something else if it is prefered.  Apparently, the author of espeak could not be contacted and espeak-ng was created a few years ago to continue development.
I have been using these packages with my screen readers for a few hours and everything seems like its working so far.