Select the language you want for Text (UI text and subtitles). In this example, we are going to use English as main voice language and Spanish as text language.
Go to the game, click on properties and select the Language you want text from: Spanish

The go to the folder: SteamLibrary\steamapps\common\Dungeons 3/Dungeons3.app/Contents/Data/AssetBundles
You will find a file named 'loca_en_text.unity3d' the name will vary depending on the selected language, loca_es_text.unity3d for Spanish or loca_fr_text.unity3d for French for example. Make a backup of this file.

Change the language again from Steam properties, so the new audio files will be downloaded example English. Wait for Steam to download the new files (aprox 300mb)
Then go back to the folder AssetBundles from Step 2, and delete or rename the 'loca_en_text.unity3d' to something else, and copy your backup file 'loca_es_text.unity3d' here, but rename it: 'loca_en_text.unity3d'

Now the game will run with the English voice but the UI will be in Spanish.

Notes:
If you change the language again from the Steam properties the files will be overriten and you need to repeat this 3 steps again.