This assumes you are willing to part with your data; fresh install means wiping previous data.
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If all steps above were performed correctly, it will NOT complain about nouveau being loaded, ignore all questions until it asks to install or configure nvidia-xconfig for you, say no at this prompt. If it fails to install, it will clearly say that the NVIDIA Driver installation has failed. If this occurs, try running the installation file again, and provide us the LAST screen before the NVIDIA driver installation fails so we can further investigate.
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I cannot stress enough that it is because the system has the onboard/offboard capability, and Ubuntu doesn't know what to do with it sometimes. It is more consistent with CentOS for it to work regardless what the primary display option in BIOS is, but Ubuntu has issues typically with onboard VGA. However, I haven't had issues with a Supermicro 4U with onboard with using the installation method listed above.
Useful POST-OS install commands to run
Allows quicker OS boot, and prevents automatic updates breaking NVIDIA driver.
[Ubuntu] Unable to manage Network via GUI
[Ubuntu] "A start job is running for wait for network to be configured"