For those who wish to play the game in their native language, which were once available with the retail version of the game. Here is a language pack patch, which allows you to alter the sound and text of the GOG version of the game to the selected one.

moddb.com/games/dungeon-keeper-2/downloads/dungeon-keeper-2-multilanguage-sound-text-mod-for-the-gog-version

Hosted on ModDB and currently supporting: Danish, Dutch, French, German, Italian, Polish, Spanish & Swedish.

Simply install the GOG release of the game and apply the patch.
It also contains the General Improvements Mod from Wyrmcast, to fix the AI in single-player.

That's a nice package.
Already got some old one, but it's prone to gone missing... so it's nice to have some form of backup