the game still checks the original registry key and not the gog supplied one

so if you want to switch the language you need to create this in regedit

Windows x86:
HKEY_LOCAL_MACHINE\SOFTWARE\Warner Bros. Interactive Entertainment\LEGOLOTR
“LanguageVal”=DWORD

Windows x64:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Warner Bros. Interactive Entertainment\LEGOLOTR
“LanguageVal”=DWORD

Danish = 406
Dutch = 413
English = 809
French = 40C
German = 407
Italian = 410
Polish = 415
Portuguese - 416
Russian = 419
Spanish = 80A