The Verge editor, Sean Hollister, tested how the game would work on the Valve handheld, and while the game had "Arkane's ancestral optimizations" and wasn't officially certified by the Steam Deck, he confirmed that the game did run on the Steam Deck — with a few minor setting changes.
It is said that the game runs at 800p resolution by default on Steam Deck, and seems to use an AMD FSR 2.1 quality setting, which does not seem to work properly on Steam Deck. So he changed the resolution to 1280 x 720p, low image quality, and the ultra performance mode of FSR 2.1. This makes the game look very mushy, but the frame rate has also been increased from 24 FPS to 48 FPS. Although it cannot be said to be smooth, it is at least able to run.
The following is a comparison chart:
Before the change
After the change
before
afterwards
Sean also recommends another tweak: changing the refresh rate to 40 Hz in the Steam Deck's quick settings menu. He said this will improve battery life and the responsiveness of the game.