Quickly change the language on macOS via terminal:
defaults write -g AppleLanguages -array xx_YY
Replace xx_YY by the desired language/locale code, i.e.: pt_BR, ca_ES and so on.
This will change the language for the whole system, so when a new app is opened, it will be displayed using the specified values. Additionally, you can check which ones are available under any app by showing its package contents. For example, in Safari you can check them under
/Applications/Safari.app/Contents/Resources. There you can locate the different .lproj folders
More info on the defaults man page
First published on April 11, 2019