While there is no permanent "free code" generator, Ubisoft occasionally offers the game for free through official promotions:

Ubisoft Connect, formerly known as Uplay, is a digital distribution platform developed by Ubisoft. It allows users to purchase, download, and manage their Ubisoft games, as well as connect with friends and join online multiplayer sessions. The platform provides a centralized hub for Ubisoft games, making it easy for users to access their game library and enjoy various features, such as cloud saves, achievements, and rewards.

If you are looking for an activation code, here is the reality of how the system works today. The Reality of "Free" Activation Codes