I have finally reached looking into this - the continuing failure to translate all strings, even when the English ts file is almost complete (testing the master branch).
It is some sort of encoding screwup - pretty much every string in the source that I can see with an accent or cap is not translated in the GUI (but the French characters do render properly so 'QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));' is taking effect).
I have spent a few hours working on this problem, and the best I have so far is the following from an lupdate *.pro call:
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lupdate warning: Codec for tr() 'UTF-8' disagrees with existing file's codec 'ISO-8859-1'. Expect trouble.
Updating 'hyne_en.ts'...
Found 1660 source text(s) (0 new and 1660 already existing)
Kept 5 obsolete entries
lupdate warning: Codec for tr() 'UTF-8' disagrees with existing file's codec 'ISO-8859-1'. Expect trouble.
Updating 'hyne_ja.ts'...
Found 1660 source text(s) (0 new and 1660 already existing)
Kept 4 obsolete entries
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There are definitely some bad strings in the ts file (obvious double-width characters), and a quick check in the source shows that bad text is around - e.g. MetadataDialog.cpp in MetadataDialog::build(),
the HelpWidget constructor call.
I plan on Thursday to kill off all bad characters in the ts file to see if this makes a difference.
This is a Debian Testing machine, so UTF-8 has been standard for about 12-13 years...