I have the South Park bundle from Steam. The Ubisoft launcher wasn’t an issue, more of a minor annoyance because you need to log into it every so often.
A bigger issue is that both Stick of Truth and Fractured But Whole suffer from random freezes that require killing the game from the Steam Deck menu. It doesn’t appear to be universal, but other folks have said the same thing on ProtonDB. Tinkering with proton versions hasn’t fixed it for me yet.