Stranger of Paradise: Final Fantasy Origin doesn't work out of the box on Steam Deck, you need a specific command line argument and GE-Proton version to get up and running, and even then you are only going to be getting 30 FPS.
Thanks to SDHQ for tweeting the additional command line required to get this up and running
Command Line Needed:
You will also need GE-Proton 7-54 to have all of your cut scenes working as well.
Ignore the tutorial section looking horrible, the rest of the game looks pretty good on the following settings beyond that point:
Low Settings Preset
FPS in-game and Steam Deck at 30 FPS
Motion Blur Off
Screen-Space Reflections off
Model Resolution scaling 80%
Chromatic Abriation off
As an extra, under general settings, turn the short soul burst animation on for smoother gameplay and battles.
If you need to install GE-Proton you can check out our video guide below