I barely passed high school French so don’t ask me! ☺
I’m assuming it has to do w/ the local settings being passed through from the os. i’d expect that java arg to do something – another idea is to find the jvm option for the local and use the blcli_setjvmoption.
I can spin up a French VM and mess around sometime… now – i haven’t messed w/ the various windows languages in a while – is there a separate ‘french’ version of the windows installer iso or it’s just the normal install w/ a language pack/locale set ?
You should be able to just install Windows normally and you can add a language pack. You can set that per profile, at least in Windows 10.