This bug report pertains to Audacity 2.2.1 running on Xubuntu 18.04.5.
I downloaded Audacity download latest version and unpacked it to
/usr/share/audacity
according to Unzipping the Manual - Audacity Manual. (nota bene: 2.4.2 apparently is the most recent version, where could I get the 2.2.1-version of the handbook?)
The directory structure there is
a@w:~$ tree -d -L 4 /usr/share/audacity
/usr/share/audacity
├── help
│ └── manual
│ ├── m
│ │ ├── images
│ │ ├── resources
│ │ └── skins
│ ├── man
│ │ └── tracks_menu_mute
│ └── manual
│ └── images
├── include
│ └── audacity
├── nyquist
│ └── rawwaves
└── plug-ins15 directories
a@w:~$
However, if I invoke the online help, I get an error message
File not found, file:///usr/share/audacity/help/manual/index.html
But
/usr/share/audacity/help/manual/index.html
exists! I can open it with mousepad. Its content is typical html code. When I double click on the file in Thunar, Firefox opens and gives me the error message
Error: File not found.
If I copy the URL
file:///usr/share/audacity/help/manual/index.html
from firefox to the clipboard and if I paste it to the URL in Chromium, the online help opens fine. What’s wrong here?