I have the same problem as mentioned in this thread. For the life of me, I can't change the locale of my fresh, hours old, Manjaro OpenRC/Cinnamon install through the Manjaro Settings Manager.
I have succesfully installed 2 languages: nl_NL and en_US. When I make any change to the locale settings in the Settings Manager, the changes disappears the moment I hit apply. No setting will stick.
I have not yet hit the lucky situation where somehow, through no reproducible set of actions, my settings will stick.
Is something crucial missing from my Cinnamon minimal install? Anyone got a clue?