I am interested too, i spend too much time at work and i would love to play it on the go.

yes it works with proton.

Yes works fine played a lot on it

Any settings you change? I Hate that the mouse cursor won't reappear. It makes all the menus tough to navigate.

Proton helps? I find it runs like absolute BUTT on my deck out of the box, but I didn't fiddle with anything.

grab cryoUtils if you havent. your gonna get the screen error but it affects nothing. i have a layout on github and on the community page that fixes the mouse.

i played grim dawn from A to Z on my steam deck LCD 256 go last year while i was travelling. The steam deck starts to struggle when you reach the last stages of the game, my advice is to decrease shadows quality, set the effects quality to minimum and REMOVE the real time damage's display.