Verified status
The publisher has announced Steam Deck Verified status for Order of the Sinking Star. That answers the certification question, but it does not supply a measured frame rate, battery-life estimate or settings benchmark.
Choosing settings
The retrieved Steam requirements still leave detailed specifications marked TBD. This site has not tested the game on a Deck, so there is no supported performance preset to recommend from those requirements.
Sources
Information checked October 2, 2026. Demo and pre-release details remain scoped to the sources described above.