I would like to install an additional ui language in Photoshop.
I have a Creative Cloud subscription, but how do I get the language pack?
German is definitely available (I'm afraid I don't know why you cannot access it)
The new Adobe Application Manager (AAM), install whatever apps you want in your primary language, then go into Preferences (upper left corner) and switch to a different language. You must have the older version which came which 4 langauge.
Log on to https://creative.adobe.com/ and download Adobe Application Manager (AAM)