DOES work on Steam Deck, ONLY if you edit the launch options to "Force the use of a specific Compatability tool" and set it to "Proton: Experimental."

FYI to those interested

Thank you for this !

The Linux version is the same and should work off the bat, just fyi

Pico-8 0.2.5 for Linux works amazingly well.  The screen and joysticks make for a match made in heaven.