If all else fails, you may want to downgrade drivers.
The problems I had with HZD began with nvidia 515.48.07; those were DLSS-specific problems (black third of the screen after displaying map).
It got worse at some point after that, and, having played again recently, I have experienced consistent crashes, usually shortly after entering gameplay, as you describe. They are fairly easy to provoke by changing upscaling method repeatedly. I observed them with a 3070 and a 4070.
Most of my playtime was with 3070+515.43.04, and it was flawless.
I hope you don’t mean “shut the whole computer down with the off button”; there are less drastic options that work for this, such as, by order of ascending severity, CTRL+ALT+ESC+click on window in KDE, CTRL+ALT+Fx + top + kill -9, CTRL+ALT+BACKSPACE (if activated; kills whole desktop), REISUB (if activated), etc.