I'm running it on a first gen Deck with absolutely no issues, and a steady framerate. Be sure to switch your graphics backend from Vulkan to OpenGL, that should fix the crashing.
The game doesn't take a lot out of the Deck, so I actually have the GPU downclocked to 800Mhz, and the refresh rate locked to 30FPS, since that's what AC runs at. I keep the CPU at normal clock because it makes the game load faster, but you can also downclock that if you don't mind the load times.