translate-shell
?You can use the translate-shell translator program as a dictionary source. It will return results from Google Translate (default), Bing Translator, Yandex.Translate or Apertium.
Translate-shell is bundled with this Flatpak. To use it in addition to the default dictionary sources, go to Dictionaries > Sources > Programs of GoldenDict, and add an item with the following settings
trans -engine google -source en -target es -show-original y -show-original-phonetics n -show-translation y -no-ansi -show-translation-phonetics n -show-prompt-message n -show-languages y -show-original-dictionary n -show-dictionary n -show-alternatives n "%GDWORD%"
Note that you should adjust the language parameters according to your needs, according to its documentation.