Question I need help troubleshooting frequent crashes on a custom built PC ?

[cloud-it]

Hi, my PC crashes frequently, primarily with BSOD.

I have assembled my own PCs for years and I have always been able to eventually resolve the issues, but this one seems beyond me.
I've purchased the components on January 2024 and I've endured the frequent crashes all this time. I would like to find and fix the root cause now.

Observed behavior:

1. The PC crashes with BSOD at random times. Sometimes it's 1 minute after boot, sometimes after a couple of hours.
2. The error codes in the BSOD vary. Some codes I remember seeing: MEMORY_MANAGEMENT, PFN_LIST_CORRUPT, ATTEMPTED_WRITE_TO_READONLY_MEMORY
3. It seems that it gets worse while I'm playing a game. I don't play resource-intense games, I mainly play turn-based games.
4. It seems that it happen with more frequency when I'm switching from one application to another one.
5. It happens almost all the time when I leave Windows idle (so it enters standby). Basically, if I leave the PC idle and I come back to it later, the greatest majority of the times I notice that it has restarted.
6. I use Ubuntu linux as well. I don't see the same crashes obviously but I do get some minor failures here and there, like a tab or two in Chrome that crashes. The problem is definitely less severe in Ubuntu.

What I have tried so far:

• Fresh re-install of Windows --> no change
• I bought a brand new pair of RAM sticks --> no change
• I bought a brand new SSD and installed Windows from scratch on it --> no change
• I've tried changing on which HDD the games are installed --> no change
• Windows Memory Diagnostics: run multiple times --> no failures
• Ran TestMem5 with various configs: the "Extreme1@anta777.cfg" does show a few errors
• Opened the case, checked all connections, cleaned-up dust --> no change
• Re-installed GPU drivers --> no change

My build:

• https://pcpartpicker.com/list/ZcLsLc
• Nothing overclocked, everything is left at default settings.
• Motherboard BIOS is updated to latest version, as are the chipset drivers.

Any help would be greatly appreciated. Thank you!