It Takes Two's Steam Deck update broke old cloud saves, but EA has an old-school workaround
It Takes Two is now fully Steam Deck verified, supports the Steam friends list, and no longer requires the EA launcher. But there's a catch.
They posted a completed save file on their website and instructions on where to save it on your PC to be able to use it. So it's not your own cloud save, but it does give you a completed save.