Trying to Launch Siege on a Different Ubisoft Account Without Reinstalling

I just bought Rainbow Six Siege on a different Ubisoft account, but my main account (the one I previously played on) is linked to Steam. Since the game is already installed via Steam, I tried using the “Locate Installed Game” option in Ubisoft Connect on my new account to avoid downloading it again.

However, when I select the Steam installation folder, it says “Failed to validate game files.” And when I launch the game through steam whilst logged into my new account, it’ll say something about it linking to my steam and I’m scared that means it’ll kick me out my main.

Is there a way to make Ubisoft Connect recognise the existing files without having to redownload the entire game? Sorry if the explanation isn’t clear—basically, I want to launch the Steam-installed game through my new Ubisoft account.

Any help would be appreciated!