The Unity Localization integration lets Ultimate Inventory System menus display translated Item names, descriptions, and interface labels without renaming the Item Definitions that gameplay uses. . . .
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If you wish to use another localization package like the i2 plugin, you'll need to make the integration yourself. In which case I'd recommend downloading the unity localization integration and check out the code to see how we did it there. Most likely the your solution will be very similar.