If you use Creative Cloud Packager to create a package and choose the Match OS option, the products are installed in the language based on the locale settings on the host system.
When the installer is run, it checks for the locale on the host system. It must be noted that the locale check is done at the system level. This implies that if, on a host system, the locale for which the products need to be installed is set for a user (or set of users), the products will not be installed in that language but will be installed in the locale that is set at the system level.
To ensure that the products are installed in a specific language, you need to ensure that locale is set at the system level.
For the Windows OS, perform the steps detailed the Microsoft document to change the locale and region.
For the MAC OS, perform the following steps:
This section details the steps to change the locale and region on a computer running MAC and Windows OS.
Use the following command to change the OS locale at the system level:
sudo defaults write .GlobalPreferences AppleLocale de_DE
The new locale would be then sniffed by Creative Cloud Packager installer correctly.