I just tested it. They use built-in Microsoft Sam as TTS (at least in Windows), old and awfull.
TTS in the Edge is pretty close to the bleeding edge. It's good. Both English and Russian. And Edge is still a gorgeus Chromium without recent time UI degradations and without ad- and privacy- blocker intolerant management.
Personally i have a prejudice against Firefox for subjectively poor and ugly UI and old scars from their rendering issues.
TTS in the Edge is pretty close to the bleeding edge. It's good. Both English and Russian. And Edge is still a gorgeus Chromium without recent time UI degradations and without ad- and privacy- blocker intolerant management.
Personally i have a prejudice against Firefox for subjectively poor and ugly UI and old scars from their rendering issues.