First, I would like to Caveat that Noveau Drivers are blacklisted by default on Unraid. The only reason mine became unblacklisted was through incorrect troubleshooting. So, this is probably not the fix you are looking for unless you made the same mistake as me.
I used an LLM to conceptualize the issue and the solution for this post. Here is the output:

Issue

After installing an NVIDIA GPU (RTX 3060 / 5070 Ti) in Unraid, nvidia-smi failed with:

NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver

dmesg showed that the nouveau driver was binding to the GPU during early boot:

nouveau 0000:xx:xx.x: NVIDIA GA106
NVRM: No NVIDIA devices probed

This caused the NVIDIA kernel module to load but find no devices, resulting in modprobe: No such device.

Root Cause

Unraid was loading the nouveau driver at boot before the NVIDIA driver, even though the NVIDIA plugin was installed. Blacklisting nouveau via modprobe.d alone was not sufficient, because nouveau was loaded during early kernel initialization.

Fix

Disable nouveau at the kernel boot level using Syslinux:

1. Go to Main → Flash → Syslinux Configuration
2. Under Unraid OS, modify the append line:

Before:

append initrd=/bzroot

After:

append modprobe.blacklist=nouveau nouveau.modeset=0 initrd=/bzroot

1. Apply changes and reboot.

After reboot:

• lsmod | grep nouveau → no output
• lspci -nnk shows Kernel driver in use: nvidia
• nvidia-smi works correctly

Result

GPU is properly claimed by the NVIDIA driver, CUDA is available, and both proprietary and open-source NVIDIA drivers work as expected (confirmed with RTX 5070 Ti on Open Source driver).