You are right: in 6.1.5 the offline help opens using a browser and in the URL field it starts with "file ..."
In an 6.0.7 installation on Linux Mint 19, where the offline help works, the file opens other than with a browser.
And in the 6.0.7 installation on a Windows 7 Workstation the computer tells me
"offline help is not installed"
HOWEVER, I installed both Japanese and English versions, each one alone and together,
tried to fiddle with the language setting (currently: interface = English, locale = Japanese), but that did not change anything.
This "offline help is not installed" is what I would like to change.
Have not yet had the time to upgrade to 6.1.5, but should it not be possible to install the offline help also for 6.0.7?
Thank you.
Thomas