I have a Mac Pro 2008 (a.k.a MacPro3,1), with Ubuntu 20.04 installed in EFI mode on it's own unencrypted SSD. The graphics card is a Quadro K5000 which has been flashed with Mac EFI compatible firmware. The card works perfectly in OS X El Capitan, and when using the nouveau drivers I can see the desktop. When I try installing the proprietary driver, however, I see only a black screen after booting.
According to NVIDIA's website, the Quadro K5000 is supported in Linux with the driver v460.39. This is slightly newer than the version provided by Ubuntu, but since this card is a few years old (released in 2012) I believe it should work with the package nvidia-driver-460.
Rather, I believed it should work. Investigating further, NVIDIA's website claims the newest Linux driver for the Quadro K5000 Mac Edition is v410.73. So it should be a simple matter of installing nvidia-driver-410 right? Well, there doesn't seem to be a package with that name provided by Ubuntu.
Right now I am trying out older drivers, starting with nvidia-driver-450, to see if any of them work with my setup. If I find a good one I'll update. Is it possible to fix my black screen issue while using the 460 drivers?
Update: The 450 drivers don't seem to work, same black screen. This time I remembered about dmesg and decided to check the output. I noticed these two lines:
[ 23.693765] nvidia-modeset: WARNING: GPU:0: Lost display notification (0:0x00000000); continuing.
[ 224.531265] nvidia-modeset: WARNING: GPU:0: Unable to read EDID for display device DVI-I-0
I'm not sure if this is relevant but my monitor is a 23 inch aluminum Apple Cinema Display.
This one can be done from recovery mode.
Restart your computer and press the SHIFT button while booting. This should offer you a text screen where you can pick recovery mode.
From there, drop to a prompt and simply remove the Nvidia drivers you added. It's possibly a good idea to reboot at this point rather than installing new drivers, just to be sure.
When you reboot, open the terminal and enter:
Press ENTER and let apt do its thing, rebooting when it has finished. When you reboot, you should have the proper drivers installed and running properly.