I plan to work on this feature next, based on my experience on setting the correct settings on vanilla gnome installed with manjaro-architect. To get the correct settings, I had to
- generate an extra (finnish) locale
- choose english for language and finnish for units in gnome settings
So, ideally manjaro-architect should generate two locales when needed and set one for language and one for units and stuff. I think Calamares gets the other locale based on your time zone choice. That is challenging to implement, because it would require a static mapping of all time zones to certain locales. Possible still, because the output of
timedatectl list-timezones is not that long. If someone can provide an list of correct locales for all time zones, I can try this approach.
The other option is to make the locale choice a multi selection operation. Then, at minimum add locale files to the file editing list. Or, if you chose more than one locale initially, set one for language and one for the other variables.
Any help and ideas is appreciated. @Beardedgeek72, you might be interested in this.