The U-Play launcher included in the Steam download is outdated and broken. To get around this, follow theses steps.

1: You will need the Ubisoft Connect Launcher already installed. I used the nonsteamlaunchers program to download it. 2: Cannot skip: You will need to download and open the game once to get this error. Restart deck. 3: Enter Desktop mode, find the Compdata path for the game, open c drive, program files (x86). Mine is /compatdata/33230/pfx/drive_c/Program Files (x86)/Ubisoft/. 4: Delete everything in this Ubisoft folder. Keep this folder open, you are going to need it again. 5: Find your compdata folder for the Ubisoft launcher. Since I used the nonsteamlauchers program to install this, my file path was /compatdata/NonSteamLaunchers/pfx/drive_c/Program Files (x86)/Ubisoft/ 6: Right-click copy the folder, go back to the folder for the game, paste the launcher files here. 7: Wait for files to copy, restart steamdeck.

Game should be working now.

It runs good, just the launcher prevents it from working without deleting the Ubisoft launcher, and installing new versions in its place.