Initially Ubisoft said it wouldn't be supported, then they said it would be and now Valve have said that Assassin's Creed Shadows is Steam Deck Verified. This new status was first noted in my article on the Steam Deck hitting 18,000 playable games but it's easy to miss if you skipped over it.
From the news post:
We have some exciting news to share: our talented developers gave Steam Deck players the option to play Assassin’s Creed Shadows at launch ; despite initially announcing we wouldn’t be able to support until later. Indeed, the team made great progress over the past few weeks and was able to make it happen for launch, despite the fact the team thought it would not be the case. It is now fully confirmed the game is "Steam Deck verified" for launch on March 20th.
We know many of you who play on Steam Deck have requested this, so we’re thrilled to be able to bring Shadows to this platform. While graphical settings will be locked at launch, you’ll be able to choose the upscalers you want, and we’re looking into providing further options in future updates.
You'll most likely be able to unlock the graphical settings if you set the "SteamDeck=0 %command%" launch option. Unless they're locking it differently to other developers who have done the same.

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With it being Steam Deck Verified, that's good news for Desktop Linux players too, since this means it will work fine on your more powerful systems. Valve verified it against the latest Proton 9.0-4.
For the Steam release it will launch with support for collectible virtual trading cards, badges, emoticons, and background images exclusively on Steam. The game does have Denuvo though, so be careful swapping any Proton version around, as you can end up locked out for a day.
What do we think? Will it see a nice clear 30FPS at least?
While graphical settings will be locked at launch, you’ll be able to choose the upscalers you want, and we’re looking into providing further options in future updates.
It's a weird approach to even consider locking the settings in the first place. It would be much better to have good automatic detection of capabilities that would work on all the range of PC hardware that's out there to set the configuration automatically, and still allow the user to set things to their preference. Like most PC games have done for many years.

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