Add New Localisation Language to Qt6

Luganda01

Hello,

The instructions in the wiki Qt Localization show how to update or add to translations for existing languages in Qt5 and Qt6. However they only show how to begin translations for a new language in Qt5 but not in Qt6.
If I attempt to use

make ts-untranslated

it returns

make: *** No rule to make target 'ts-untranslated'.  Stop.

The instruction

cd qttranslations; <qt-installation>/bin/qt-cmake . -G Ninja; ninja ts-<lang>

seems to be clearly for an existing language. If I run it with 'ts-untranslated' it returns

-- Configuring done (0.8s)
-- Generating done (0.1s)
-- Build files have been written to: /home/muwawa/nls/Ebikyusibwa/Qt/build/qt6/qttranslations
ninja: error: unknown target 'ts-untranslated'

It gives similar output if I run it with 'ts-lg', where 'lg' is the two letter code for the language (Luganda) that I wish to start translating into.
Could somebody advise me of the correct way to add a new language in Qt6 please?
I am using Qt 6.7.3.

Regards,

Kizito