I had the same problem I could play for hours and then freeze>blackscreen>bsod half second>reboot with no dump files, then after the update it became more consistent in the sense i was crashing as soon as entering sandbox or spectate a match, that at least gave me something consistent to work...
Lowering a bit graphic settings and creating a more conservative profile for the GPU (undervolting+underclocking, 3080) solved the issue and stabilized the game for me at the cost of 10-15 fps.
I could not replicate the crashes and reboots outside of the game and the system passed stress tests...
Check your system for stability with some stress tests (furmark, OCCT).
If the system is stable but your pc shuts off only in Deadlock (like mine did, my screen freezed for 2-5 sec then reset) you may try to undervolt+underclock your GPU, I did that and in my case it stabilized the situation at...
I had the exact same problem, lowering a bit graphic setting and undervolting+underclocking further my gpu (3080) stabilized the situation at the expense of some performance (10-15fps), for your 3090 should be even less noticeable. You may give it a try.
Setting everything to a minimum seemed to prevent the crash for me, and the fact the pc was freezing and resetting with no crash dumps made me think of a hardware instability (my GPU). If your crashes are different than this it may be all a different story tho, and underclocking/volting as you...
I could not find the crash dumps aswell.
My GPU was already undervolted and stable in other applications and tests, and my PSU was more than enought aswell. What I'm trying to say is that while your system may seems perfectly stable in general this game at this stage is a lot more unstable by...
I was crashing randomly before the update (complete freeze and system reset), and always as soon as i entered the sandbox after the update.
In my case lowering the graphic settings a bit + undervolting and underclocking the gpu seems to have stabilized the situation.
No luck disabling XMP, but i was able to stabilize the game undervolting and underclocking further my gpu and lowering a bit the video quality settings.
Now i don't know if its my gpu that is starting to deteriorate (3080) or just the game, the GPU passes stress tests and seems perfectly stable...