Please confirm if you tried with driver 520.56.06.
This driver fixed issue for users reported on another thread.
[Bug Report] Black X11 Screen and partial lockup when upgraded to 515.76 and dual RTX3060 - Graphics / Linux / Linux - NVIDIA Developer Forums
Thank you for your prompt response!
It looks like you shared a workaround, which I appreciate to become unblocked, but I do not think this can be considered a fix.
When is Nvidia going to fix this problem?
In other words, when can users expect to install cuda from official package sources and not have breakage?
sudo apt install cuda
Thanks again for your support!