Wait, this is LibreWolf we're speaking about. Have you unchecked these two? (see screenshot)

UPDATE: The upper checkbox seems to flip browser.translations.enable in about:config. Librewolf even demands you do a full browser restart after unchecking. Combined with the name of the property, I think it's a win for you! I mean, that this thing really disables translations from ever executing.
UPDATE 2: Admittedly it's not pre-disabled though. But clearly exposed in the settings.