DX12 API is super bad. I tested most of protons and for DX12 best was:
GE-7.19
and
Proton Experimental Bleeding Edge

happens on experimental too
Seems like MESA bug as I am unable to reproduce on nvidia rtx 3070 with just 8gb of vram.
EDIT: On Ready or Not however it fills my 8GB when ran with VKD3D and game becomes choppy, but no crashes.
Something updated and the crashes no longer occur, nice!
I take that back, just "ran out of memory" whist only using 47% of my vram
Also having this issue with Grounded
proton experimentalx2 2022-08ge-proton7-28x1 2022-07
Compatibility Report
System Information
steam-581320.zip
I confirm:
Symptoms
Reproduction
The last few days I have played these two titles in DX12 interchangeably, back to back
I am not sure if it is necessary to play the games back to back to reproduce the bug, or it simply occurs on all dx12 titles at random times after a period of gameplay
Launch and play ready or not, selecting dx12 from the popup when prompted at launch time
After a couple missions I get the exact same out of memory popup pictured above
Launch and play insurgency sandstorm with -dx12 in the launch parameters, after a random amount of time (0-3 games?) the above popup is shown
If I play the games in dx11 (sandstorm without -dx12, and clicking dx11 in the popup for ready or not), they run fine (although at lower frame rate)
I'll try find some more dx12 games to find if the pattern extends to all of them, or if it's just something odd about these two. I assume there's something different about my system because I've run into a few others with the 6900XT that don't have this problem playing dx12 games.