Ubuntu 20.04 and GeForce 2080Ti (+nvidia drivers 440 or 450)

I am trying to get Ubuntu 20.04 to run on a computer (desktop) with a GeForce 2080Ti and I had no luck with various versions of the nvidia drivers.

I installed the latest drivers 450.66 which corresponds to my graphic card using the install program proposed (no errors in the process). But still, no luck:

nvidia-smi --> No devices were found.

In /var/log/Xorg.0.log --> (EE) Failed to initialize the NVIDIA GPU at PIC:7:0:0.

dmesg --> NVRM: GPU 0000:07/00.0: RmInitAdapter failed!

==== Other info that could help:

I have a GUI when I prime-select intel
Secure boot is disabled
nouveau is blacklisted

Thanks for help,nvidia-bug-report.log.gz (106.1 KB)

I continued to look for solutions… I have added mem_encrypt=off but I still get the very same output. Any ideas someone? Could it be a hardware problem?