What do I need llvmpipe for?

For unknown reasons only my main monitor functions. The other is dark. Applications such as the Firestorm Viewer that make heavy use of GPU run too slowly to be useful. When I attempt to run: nvidia-smi I get the below:

$ nvidia-smi
NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

$glxinfo -B
name of display: :1
display: :1  screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: Mesa/X.org (0xffffffff)
    Device: llvmpipe (LLVM 13.0.1, 256 bits) (0xffffffff)
    Version: 22.0.5

For some unknown reason my computer decided to start using llvmpipe instead of the also installed Nvidia graphics drivers. I do not know how llvmpipe got installed. I am concerned that if I remove it I will break something that depends on it. How might this llvmpipe have gotten installed? Is it something I really need?

I have seen in other threads a solution that requires disabling secure boot. I am not comfortable opening up that vulnerability. What alternatives are there?

llvmpipe is the fall-back software renderer when the real graphics driver is broken/defunct. You never remove it but make your graphics driver work again instead.
Please run nvidia-bug-report.sh as root and attach the resulting nvidia-bug-report.log.gz file to your post.

So you think my GTX 1080 Ti hardware has failed? That it has failed would be consistent with this problem disappearing for a few days, reappearing, and then disappearing for one day, and now its failing hard.

I have had this board for about 10 years.

The report our requested:
nvidia-bug-report.log.gz (122.8 KB)

I much appreciate your help with this.

Hardware is fine. Ubuntu seems to have an issue with kernel upgrades, instead of the stock 5.15 kernel you got pushed to a 5.17-oem kernel without headers. You’re the third user here now.
Since you have secure boot enabled, your modules need to be signed. Unfortunately, I can’t see whether you had pre-compiled, signed modules or module signing set up before the upgrade.
Please try installing the kernel headers first
sudo apt install linux-headers-$(uname -r)

Thank you for this. The header installation worked. I now have both monitors working, and the graphics card fully functional. I am much relieved I will not have to replace this graphics board.

I chose a Unix OS for performance, and privacy, reasons I very much need these. But I find that very often something goes wrong with it, and finding out what to do about it each time costs significant time. This headers issue is just the latest example of this.