Ah sorry, I merged the branch to dev and removed it 
, so it’s:
curl -sSfL https://raw.githubusercontent.com/MichaIng/DietPi/dev/.conf/dps_176/mycroft.conf -o /etc/mycroft/mycroft.conf
That somehow matches my experience when using the old /etc/asound.conf without conversions, as then, if the sound card does not support the given wav format, if fails (silently in my case) and otherwise it succeeds. Also some audio sources are mp3 or ogg files, which always succeed, so only wav is affected. But it can be something different.
The British Male voice works fine in your case? I tried on different machines and different Debian versions and if fails everywhere with the same error message (/var/log/mycroft/audio.log) that was reported here already: Upgraded ubuntu from 18.04 to 20.04, no more TTS - #9 by dan