User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:92.0) Gecko/20100101 Firefox/92.0
Steps to reproduce:
Using the firefox snap, open the devtools console, and enter:
speechSynthesis.speak(new SpeechSynthesisUtterance("Testing 1 2 3"));
Nothing (no text is being spoken).
speech-dispatcher should be speaking "Testing 1 2 3".
This is a snap-specific issue, speech synthesis works well with an unconfined build of firefox. More details at https://forum.snapcraft.io/t/firefox-snap-speech-dispatcher/6165.