I had my Macbook running Ubuntu MATE 15.10 perfectly and decided to be smart and switch from the built in nvidia driver from additional drivers to the one on nvidia’s website for my graphics card which is a geforce 8600GT. I rebooted into grub and ran the .run file as root in grub recovery and the first red flag was the warning that my distribution script failed and then I kept going and it asked to build a dkms kernel module and then it wrapped up when it was finished. I rebooted and grub did load and I took out quiet splash so I could have a look and my system hangs when LVM tries to load… I rebooted and tried to purge the nvidia drivers and reboot but whether wired or WiFi I cannot get grub recovery to connect my networking so I’m gills up and I don’t know how to get x server back up and running at least with the nouveau driver. I have a live USB but I’d rather not format if I can learn to do this in case I need to ever do it again in the future. Any help you can provide will be seriously appreciated. I’m running Ubuntu MATE 15.10 64 bit on a Early 2008 Aluminum Macbook Pro model 4,1
What about console (tty)? You should still have a wired connection there.
Either at grub boot or at the login screen, press:
Ctrl + Alt + F1
and login
Will the cntrl alt F1 work on a Mac?
Are macs that different? If they are, you will need to wait for someone else to come along. I have owned just one apple in my life and it was a Apple Lisa 
If you can get into recovery mode, follow the removal commands from this thread:
Awesome! Thanks @wolfman!!
Great!, please mark best answer so it helps others!. 
You got it. I was able to install the nvidia driver and enable full 3d acceleration on the Geforce 8600M GT. The process was relatively straight forward with this Mac, if anyone gets stuck I would be happy to help. I will likely write a tutorial on this one soon, its a “special” process LOL 
thanks again @wolfman
And how you did it? I didn't manage to make it work. I am getting black screen when I install the nvidia driver.
Welcome @Raycho_Mukelov to the community!
Yep, typical nVidia as usual.
One advice though: If you don't do gaming or CUDA based stuff, don't use the proprietary nVidia driver. It is faster but qualitatively worse than the open Nouveau driver.
That said, follow this link for possible solutions:
More links and solutions:
https://ubuntu-mate.community/t/black-screen-issues
https://ubuntu-mate.community/t/black-screen-after-boot-on-18-04-with-nvidia
https://ubuntu-mate.community/t/black-screen-after-changing-graphic-card
https://ubuntu-mate.community/t/black-screen-missing-login-screen
https://ubuntu-mate.community/t/black-screen-no-login-prompt-after-latest-nvidia-update
https://ubuntu-mate.community/t/get-black-screen-lightdm-cannot-start