Hi,
I built Audacity following the Steve guide here:
https://forum.audacityteam.org/t/building-audacity-2-4-2-on-ubuntu-20-04/57719/1
Everything is fine but the manual.
I downloaded it from the Foss site an used the code:
sudo unzip audacity-manual-2.4.2.zip -d /usr/local/share/audacity/help
But Audacity can’t find the manual.
I saw the terminal and I found an error on the path. It shows:
/usr/local/share/audacity**/help/help/**manual/
So I deleted the /help on the code and now Audacity finds the manual:
sudo unzip audacity-manual-2.4.2.zip -d /usr/local/share/audacity
Hope this is helpful for someone
(And maybe Steve can fix this on the build guide 
)