I've checked the range of supported languages for Dolphin Supernova and they don't support Afrikaans,
https://yourdolphin.com/product/languages?pid=4
But this website https://www.webbie.org.uk/links.htm
mentions
$1> These free voices can be used with the Thunder or NVDA screenreaders. Includes **Afrikaans**, Bosnian, Czech, Greek, Esperanto, Finnish, Croatian, Hungarian, Kurdish, Romanian, Slovak, Serbian, Swedish, Swahili, Tamil, Turkish.
However on the eSpeak sourceforge page it carries the caveats
> Languages. The eSpeak speech synthesizer supports several languages, however in many cases these are initial drafts and need more work to improve them. Assistance from native speakers is welcome for these, or other new languages. Please contact me if you want to help.
>eSpeak does text to speech synthesis for the following languages, some better than others.