Stadia has launched streaming support for a Ubisoft+ subscription in the United States.
A Stadia Pro subscription is not required to play Ubisoft+ over Stadia. A Ubisoft+ subscription, for $14.99 a month, is required.
Ubisoft+ offers unlimited access to over 100 games, including day-of-release new games, and full access to premiere editions of games such as season passes and expansions.
To gain access to Ubisoft+:
Ubisoft+ is also available for Amazon Luna.