For AC Brotherhood, I wanted to use cheats on it, but there is none for Ubisoft, so I am curious to why there isn’t one
Trainers are only made if the game is popular enough on that particular platform with the overall WeMod community. Aside from that, back in 2010, when the game was released, Uplay was actually extremely unpopular because of their major limitations, such as requiring users to have a constant connection to the internet, so most people bought the game elsewhere instead. In recent times, Uplay are slowly improving their public relations with players.
Read this recent post for how getting trainers made and updated works: Vampyr for Windows suggestion - #2 by Ravenfyre.
You can attempt to use the Steam trainer by pressing the fix button and link the Uplay version’s .exe to the trainer. But there’s no guarantee it’ll work flawlessly, if at all,