Problem

Reference Data Management (RDM) accommodates localization (in U.S. usage, "localization"), but may unexpectedly show lookups in English even when another language (in the screenshot below, German) is desired:

Still, UI shows lookups in English:

Solution

This is very likely related to Browser settings. You just need to follow the right sequence to see the browser data in your desired language:

The desired language should be on top. If you want to see the full browser options along with the data in that language then choose the option "Goggle Chrome is displayed in this language." Otherwise, keeping that language on top also helps to see the localized data.

The UI supports only the locales listed in the documentation
https://documentation.reltio.com/localization/i18nandl10n.html?hl=en-us

Note: The translated values will be propagated to MDM only if a supported localization code is used. For the list of supported localization codes, see Internationalization and Localization.