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: Sites like Humble Bundle or Green Man Gaming offer legitimate, publisher-approved activation keys at deep discounts.
Furthermore, the version of the game you want is actually the official version. Ubisoft removed the always-online DRM in 2015. You can now buy the game, launch it, play entirely offline, and sync your save to the cloud when you reconnect.
: Steam, the Ubisoft Store, and the Epic Games Store regularly discount the game by up to 70% to 85% during seasonal sales.