Ck3 on steam deck keep crashing

FYI strictly speaking, the game is not supported on the Deck - yet, anyway. Only Ubuntu. That may or may not be related to your problem.

Are you using Vulkan or openGL as your renderer? Whichever one, try the other.

If that doesn't help,
Please attach here your Documents/Paradox Interactive/CK3/pdx_settings.txt .
From your Documents/Paradox Interactive/CK3/logs/ folder, attach here system.log , error.log

Also in Steam please click on Steam-Help-System Info, and paste everything there into a text file and attach that here.