In page there is text "Over the last couple of months we have ported the text-to-speech functionality in the Qt Speech module over to Qt 6, and it will be part of the Qt 6.4 release later in 2022." with link to https://doc-snapshots.qt.io/qt6-dev/qtspeech-index.html
This is dead link "404 - Page Not Found"

I suggest to Qt Company to use a dead link checker for website.

See the same report.